Endoscope

ABSTRACT

A lens having a quadrangular outer shape in a direction perpendicular to its center, an imaging element having a quadrangular outer shape in the direction perpendicular to the center axis, an element cover glass covering an imaging surface of the imaging element, a light guide placed outside at least one side of the lens and extending along the center axis, and a cylinder holder disposed between the lens and the light guide are disposed in a tip portion of an endoscope.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Applications (Nos.2016-087491, 2016-087488, 2016-087487) filed on Apr. 25, 2016, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to an endoscope.

2. Description of the Related Art

In the related art, a small-diameter endoscope that has a diameter ofless than 3 mm is known as illustrated in FIGS. 46 and 47 (refer to, forexample, JP-A-2008-212309). FIG. 46 is a front view of a tip portion ofa small-diameter electronic endoscope according to the related art. FIG.47 is a perspective view of a light guide fiber bundle unit in the tipportion of the small-diameter electronic endoscope. In thesmall-diameter endoscope according to JP-A-2008-212309, an outerperiphery of an observation window 501 is fitted into an insulating tube503 and a tip portion main body inner tube 505 is placed on an outerperiphery of the insulating tube 503. An outer edge of the tip portionmain body inner tube 505 is scraped off in accordance with the shape ofthe chord of an injection end face 507 and an injection end portion of alight guide fiber bundle 509 illustrated in FIG. 47 is inserted into aspace between a tip portion main body outer tube 511 and the tip portionmain body inner tube 505 in a filled state. Three regions are formed inthe light guide fiber bundle 509, that is, a hard molded portion 513 asa unit with which a space in the tip portion main body outer tube 511 isfilled, the hard molded portion 513 being hardened by an adhesive in theshape of the space, a flexible portion 517 inserted into and placed inan insertion portion in a state where the flexible portion 517 is coatedwith a flexible protective tube 515, and a transition portion 519between the hard molded portion 513 and the flexible portion 517.

In the configuration of the small-diameter endoscope according toJP-A-2008-212309, lighting member such as the light guide fiber bundle509 is placed around an objective optical system (that is, a circularlens) and the observation window 501 having a circular shape.Accordingly, the outer diameter of the endoscope increases to thatextent. The configuration in which the lighting member is placed aroundthe circular lens results in a useless space in an insertion tipsurface. Then, member placement density cannot be increased in theinsertion tip surface. In other words, a low level of space efficiencyarises, which results in disadvantages in terms of endoscope sizereduction. In addition, it is difficult to stably fix the circular lensand a quadrangular imaging element. Furthermore, it is difficult toreduce the size of the light guide fiber bundle 509 because the lightguide fiber bundle 509 is obtained by multiple bare fiber strands beingbundled up by being hardened by a low-viscosity adhesive and, as such,the area of its outer periphery increases and leaking light is likely tomove into the imaging element. This leaking light becomes stray light inthe optical system that leads to image quality deterioration.

SUMMARY OF THE INVENTION

The present disclosure has been made in view of the above-describedcircumstances, and an object thereof is to provide an endoscope withwhich stray light from lighting member can be prevented withhigh-strength fixing of a lens and an imaging element facilitated andsize reduction ensured by a useless space being suppressed based on anincrease in space efficiency in an insertion tip surface.

The present disclosure provides an endoscope provided with a lens thathas a quadrangular outer shape in a direction perpendicular to a centeraxis of the lens, an imaging element that has a quadrangular outer shapein the direction perpendicular to the center axis, an element coverglass configured to cover an imaging surface of the imaging element, alighting member that is disposed outside at least one side of the lensand extends along the center axis, and a light-shielding member that isdisposed between the lens and the lighting member.

According to the present disclosure, stray light from the lightingmember can be prevented, high-strength fixing of the lens and theimaging element can be facilitated, and size reduction is ensured byspace efficiency (that is, member placement density) improvement (thatis, suppression of a useless space) being allowed in an insertion tipsurface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall configuration diagram illustrating an example of anendoscope system using an endoscope according to the present embodiment.

FIG. 2 is a perspective view illustrating an appearance of a tip portionof the endoscope according to the present embodiment that is seen from afront side.

FIG. 3 is a sectional view illustrating a configuration example of thetip portion of the endoscope according to the present embodiment.

FIG. 4 is a sectional view illustrating a configuration example of astate where a lens and an imaging element of the endoscope according tothe present embodiment are attached via an adhesive resin.

FIG. 5 is a perspective view illustrating an appearance of the imagingelement of the endoscope according to the present embodiment that isseen from a rear side with a transmission cable connected to a conductorconnection portion.

FIG. 6 is a diagram illustrating a first example of a lens shape in theendoscope according to the present embodiment.

FIG. 7 is a diagram illustrating the first example of the lens shape inthe endoscope according to the present embodiment.

FIG. 8 is a diagram illustrating the first example of the lens shape inthe endoscope according to the present embodiment.

FIG. 9 is a diagram illustrating a second example of the lens shape inthe endoscope according to the present embodiment.

FIG. 10 is a diagram illustrating the second example of the lens shapein the endoscope according to the present embodiment.

FIG. 11 is a diagram illustrating the second example of the lens shapein the endoscope according to the present embodiment.

FIG. 12 is a diagram illustrating a third example of the lens shape inthe endoscope according to the present embodiment.

FIG. 13 is a diagram illustrating the third example of the lens shape inthe endoscope according to the present embodiment.

FIG. 14 is a diagram illustrating the third example of the lens shape inthe endoscope according to the present embodiment.

FIG. 15 is a diagram illustrating the third example of the lens shape inthe endoscope according to the present embodiment.

FIG. 16 is a diagram illustrating a configuration example of a surfaceof the lens of the endoscope according to the present embodiment thatadheres to an element cover glass.

FIG. 17 is a diagram illustrating a first example of the imaging elementof the endoscope according to the present embodiment.

FIG. 18 is a diagram illustrating the first example of the imagingelement of the endoscope according to the present embodiment.

FIG. 19 is a diagram illustrating a second example of the imagingelement of the endoscope according to the present embodiment.

FIG. 20 is a diagram illustrating the second example of the imagingelement of the endoscope according to the present embodiment.

FIG. 21 is a diagram illustrating a third example of the imaging elementof the endoscope according to the present embodiment.

FIG. 22 is a diagram illustrating the third example of the imagingelement of the endoscope according to the present embodiment.

FIG. 23 is an enlarged perspective view of a main part, in which alight-shielding member of the endoscope according to the presentembodiment is a notched holder.

FIG. 24 is a plan sectional view of the endoscope illustrated in FIG.23.

FIG. 25 is an exploded perspective view of the endoscope illustrated inFIG. 23.

FIG. 26 is an enlarged perspective view of the main part, in which thelight-shielding member of the endoscope according to the presentembodiment is a through-holed holder.

FIG. 27 is an exploded perspective view of the endoscope illustrated inFIG. 26.

FIG. 28 is an enlarged perspective view of the main part, in which thelight-shielding member of the endoscope according to the presentembodiment is a resin mold.

FIG. 29 is a plan sectional view of the endoscope illustrated in FIG.28.

FIG. 30 is an exploded perspective view of the endoscope illustrated inFIG. 28.

FIG. 31 is an enlarged perspective view of the main part, in which thelight-shielding member of the endoscope according to the presentembodiment is a pipe.

FIG. 32 is a plan sectional view of the endoscope illustrated in FIG.31.

FIG. 33 is an exploded perspective view of the endoscope illustrated inFIG. 31.

FIG. 34 is an enlarged perspective view of the main part, in which thelight-shielding member of the endoscope according to the presentembodiment is a jacket.

FIG. 35 is an enlarged perspective view of an optical fiber covered bythe jacket.

FIG. 36 is a perspective view of the tip portion of the endoscopeaccording to the present embodiment in which the imaging element and asheath are substantially in contact with each other and four corners ofthe imaging element are not chamfered.

FIG. 37 is a perspective view in which the sheath of the endoscopeillustrated in FIG. 36 is seen through.

FIG. 38 is a front sectional view including the imaging element of theendoscope illustrated in FIG. 36.

FIG. 39 is a perspective view of the tip portion of the endoscopeaccording to the present embodiment in which the imaging element and thesheath are substantially in contact with each other and the four cornersof the imaging element are chamfered.

FIG. 40 is a perspective view in which the sheath of the endoscopeillustrated in FIG. 39 is seen through.

FIG. 41 is a front sectional view including a sensor of the endoscopeillustrated in FIG. 39.

FIG. 42 is a plan sectional view of the endoscope illustrated in FIG.39.

FIG. 43 is a front sectional view in which a plurality of the opticalfibers is arranged along four sides of the imaging element of theendoscope according to the present embodiment.

FIG. 44 is a front sectional view in which a plurality of the opticalfibers is arranged along two sides of the imaging element of theendoscope according to the present embodiment.

FIG. 45 is a diagram for showing the length of the diameter of theoptical fiber of the endoscope according to the present embodiment.

FIG. 46 is a front view of a tip portion of a small-diameter electronicendoscope according to the related art.

FIG. 47 is a perspective view of a light guide fiber bundle unit in thetip portion of the small-diameter electronic endoscope.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment (hereinafter, referred to as “the present embodiment”)that specifically discloses an endoscope according to the presentinvention will be described in detail below with reference toaccompanying drawings with excessively detailed description omitted insome cases. Examples of the excessively detailed description includedetailed description of matters that are already well known andrepetitive description of configurations that are substantiallyidentical to each other. This is to avoid a long and tedious descriptionand allow those skilled in the art to better understand the followingdescription. The accompanying drawings and the following description arefor those skilled in the art to sufficiently understand the presentdisclosure, and the subject matter described in the scope of claims isnot limited by the accompanying drawings and the following description.

A basic configuration example common to the endoscope according to thepresent embodiment will be described first. Configuration examples referto configuration requirements that the endoscope according to thepresent invention can be provided with. It is not ruled out that theendoscope according to the present invention is provided with thefollowing respective configuration examples in an overlapping manner.

Basic Configuration Example

FIG. 1 is an overall configuration diagram illustrating an example of anendoscope system using the endoscope according to the presentembodiment. An overall configuration of an endoscope system 13 includingan endoscope 11 and a video processor 19 is illustrated in FIG. 1, whichis a perspective view.

Directions used for the description in the present specification followthe illustration of directions in each of the drawings. In theillustration, “up” and “down” correspond to above and below the videoprocessor 19 placed on a horizontal plate, respectively. “Front (ahead)”and “rear” correspond to a tip side of an insertion portion 21 of anendoscope main body (hereinafter, referred to as the “endoscope 11”) anda base end side of a plug portion 23 (that is, the video processor 19side), respectively.

As illustrated in FIG. 1, the endoscope system 13 is configured toinclude the endoscope 11 and the video processor 19. The endoscope 11is, for example, a flexible mirror for medical use. The video processor19 performs known image processing or the like on a still image or amoving image that is obtained by imaging of an inner portion of anobject of observation (such as a blood vessel in a human body). Theendoscope 11 is provided with the insertion portion 21 and the plugportion 23. The insertion portion 21 extends substantially in afront-rear direction and is inserted into the inner portion of theobject of observation. A rear portion of the insertion portion 21 isconnected to the plug portion 23.

The video processor 19 has a socket portion 27 that is open to a frontwall 25. A rear portion of the plug portion 23 of the endoscope 11 isinserted into the socket portion 27. This insertion allows the endoscope11 to send and receive electric power and various signals (such as avideo signal and a control signal) to and from the video processor 19.

The electric power and the various signals described above are guidedfrom the plug portion 23 to a soft portion 29 via a transmission cable31 (refer to FIG. 3 or FIG. 4) inserted into an inner portion of thesoft portion 29. Image data output by an imaging element 33 disposed ina tip portion 15 is transmitted from the plug portion 23 to the videoprocessor 19 via the transmission cable 31. The video processor 19performs the known image processing, such as color correction and tonecorrection, on the image data transmitted from the plug portion 23 andoutputs the image-processed image data to a display device (notillustrated). The display device is a monitor device that has a displaydevice such as a liquid crystal display panel and displays an image of asubject imaged by the endoscope 11 (such as image data showing anappearance inside a blood vessel of a person who is the subject).

The insertion portion 21 has the flexible soft portion 29 of which arear end is connected to the plug portion 23, and the tip portion 15that leads to a tip of the soft portion 29. The soft portion 29 has anappropriate length responding to various types of endoscopy, endoscopicoperations, and the like. Coating performed on an outer periphery of anet covering an outer periphery of a spirally wound metal sheet is anexample of what constitutes the soft portion 29 and the soft portion 29is formed to have a sufficient level of flexibility. The soft portion 29provides connection between the tip portion 15 and the plug portion 23.

The endoscope 11 according to the embodiment that is to be describedbelow can be inserted into body cavities that have small diametersbecause the insertion portion 21 is formed to have a small diameter. Thesmall-diameter body cavities are not limited to blood vessels in humanbodies and include, for example, the ureter, pancreatic duct, bile duct,and bronchioles. In other words, the endoscope 11 is capable of allowinginsertion into blood vessels, ureters, pancreatic ducts, bile ducts,bronchioles, and the like in human bodies. In other words, lesions inblood vessels can be observed with the endoscope 11. The endoscope 11 iseffective for arteriosclerotic plaque identification and can also beapplied to endoscope-based observation during cardiac catheter tests.Furthermore, the endoscope 11 is effective for thrombus andarteriosclerotic yellow plaque detection. In arteriosclerotic lesions,color tones (white, light yellow, and yellow) and surfaces (smooth andirregular) are observed. In the thrombus, color tones (red, white, darkred, yellow, brown, and mixed) are observed.

The endoscope 11 can be used for diagnosis and treatment of renal pelvicand ureteral cancers and idiopathic renal bleeding as well. In thiscase, the endoscope 11 is inserted from the urethra into the bladder andthen is moved into the ureter. Then, the insides of the ureter and therenal pelvis can be observed.

The endoscope 11 can be inserted into Vater's papilla open to theduodenum, too. Bile is produced in the liver and discharged from Vater'spapilla in the duodenum through the bile duct and pancreatic juice isproduced in the pancreas and discharged from Vater's papilla in theduodenum through the pancreatic duct. The endoscope 11 is capable ofallowing bile duct or pancreatic duct observation by being inserted fromVater's papillae as opening portions in the bile and pancreatic ducts.

The endoscope 11 can be inserted into the bronchial tubes as well. Theendoscope 11 is inserted from the oral cavity or nasal cavity of aspecimen (that is, a subject undergoing a medical procedure) in a supineposition. The endoscope 11 is inserted into the trachea, while viewingthe vocal cords, past the pharynx and larynx. The bronchial tubes becomethin every time they branch. With the endoscope 11 that has a maximumouter diameter Dmax of less than 2 mm, for example, lumen confirmationis possible to the point of subsegmental bronchi.

Hereinafter, the various configuration examples of the endoscopeaccording to the present embodiment will be described. The endoscope 11according to the present embodiment is capable of having each of theconfigurations ranging from first to twentieth configuration examples.

The term of “adhesive” in the following description is not limited tothe strict sense of the word, that is, a substance used for adhesionbetween surfaces of solid matter. Instead, the term is used in a broadsense of the word, that is, a substance which can be used for bondingbetween two materials or, in a case where a cured adhesive has highbarrier properties with respect to gas and liquid, a substance which hasa function as a sealant.

First Configuration Example

FIG. 2 is a perspective view illustrating an appearance of the tipportion 15 of the endoscope 11 according to the present embodiment thatis seen from a front side. FIG. 3 is a sectional view illustrating aconfiguration example of the tip portion 15 of the endoscope 11according to the present embodiment. In the endoscope 11 illustrated inFIG. 2, the maximum outer diameter Dmax of the tip portion 15illustrated in FIG. 3 can be formed to have a range of a finite diameterto 1.0 mm, which is equivalent to the diameter of a circle circumscribedabout a substrate of the imaging element 33 that can be diced.

In the endoscope 11 according to the present embodiment, an imagingelement that has one side having a dimension of 0.5 mm or less is usedas the imaging element 33 that has a square cross section in a directionperpendicular to the direction of an optical axis or an axial directionthrough a center of a lens (a center axis of the lens). Accordingly, theimaging element 33 has a diagonal dimension of approximately 0.7 mm inthe endoscope 11, and the maximum outer diameter Dmax can be 1.0 mm orless with light guides 57 (for example, φ50 μm) as lighting memberincluded.

As described above, the maximum outer diameter Dmax is less than 1.0 mmin the endoscope 11 according to the first configuration example, andthus insertion into, for example, the blood vessels in the human bodycan be further facilitated.

Second Configuration Example

In the endoscope 11 according to the present embodiment, the endoscope11 according to the second configuration example has the substrate ofthe imaging element 33 formed in a square shape and conductor connectionportions 49 placed at four corners of the substrate of the imagingelement 33 as illustrated in FIG. 5. One of the conductor connectionportions 49 is formed in, for example, a circular shape. The fourconductor connection portions 49 are placed at the four square corners.As a result, the four conductor connection portions 49 can be placedwith a maximum distance of separation from one another.

In the transmission cable 31, conductors of respective electric powerand signal lines that are electric wires 45 are covered by insulatingcoatings. The four electric wires 45 are placed in two, upper and lower,layers with two of the four on the left and the other two on the right.Outer peripheries of the insulating coatings are bundled up by an outercovering, which results in the single transmission cable 31. Therespective conductors are formed in the shape of four parallel straightlines in a state where the insulating coatings are peeled off. Tips ofthe conductors of the electric wires 45 are connected to the conductorconnection portions 49 by soldering. The imaging element 33 and thetransmission cable 31 are covered by a mold resin 17 as illustrated inFIG. 3. Accordingly, the conductor connection portions 49, theconductors, the insulating coatings of the electric wires 45, and theouter covering of the transmission cable 31 are embedded in the moldresin 17.

In the endoscope 11 according to the second configuration example, thefour conductor connection portions 49 can be placed at the four cornersof the substrate of the imaging element 33 as described above.Accordingly, the four conductor connection portions 49 can be placed onthe square substrate of the imaging element 33 at a maximum distancefrom one another and in an equally separated state as illustrated inFIG. 5. Accordingly, two of the conductor connection portions 49 thatare adjacent to each other are not connected to each other by solderingin a soldering process, ensuring of an insulation distance isfacilitated, and a reduction in the diameter of the tip portion 15 canbe facilitated.

Third Configuration Example

FIG. 4 is a sectional view illustrating a configuration example of astate where a lens 93 and the imaging element 33 of the endoscope 11according to the present embodiment are attached via an adhesive resin37. As illustrated in FIG. 4, the endoscope 11 according to the thirdconfiguration example is provided with an objective cover glass 91, anelement cover glass 43, the imaging element 33 where an imaging surface41 is covered by the element cover glass 43, the lens 93 pinched betweenthe objective cover glass 91 and the element cover glass 43 with itsoptical axis corresponding to the center of the imaging surface 41, anaperture 51 disposed between the objective cover glass 91 and the lens93, the adhesive resin 37 fixing the lens 93 and the element cover glass43, and an air layer 95 disposed between the lens 93 and the elementcover glass 43.

A small charge coupled device (CCD) or complementary metal-oxidesemiconductor (CMOS) imaging device that has a square shape when seenfrom the front-rear direction is an example of what constitutes theimaging element 33. In other words, the imaging element 33 has a squareouter shape in a direction perpendicular to the axial direction throughthe optical axis or the lens center of the lens 93. In the imagingelement 33, light incident from the outside passes through the aperture51 disposed between the objective cover glass 91 and the lens 93, andthen the light is imaged on the imaging surface 41 by the lens 93 afterthe passage. In the imaging element 33, in addition, the imaging surface41 is covered by the element cover glass 43. The element cover glass 43has a square outer shape in the direction perpendicular to the opticalaxis. The length of one side of the element cover glass 43 is equal tothe length of one side of the imaging element 33.

A UV-curable and thermosetting resin is an example of what constitutesthe adhesive resin 37. It is preferable that the adhesive resin 37 islight-transmissive and has a refractive index close to that of air. In acase where the UV-curable and thermosetting resin is used as theadhesive resin 37, an outer surface part can be cured by ultravioletirradiation and an inner portion of a filling adhesive that cannot beirradiated with ultraviolet rays can be cured by heat treatment. Theadhesive resin 37 fixes the lens 93, the optical axis of whichcorresponds to the center of the imaging surface 41, to the elementcover glass 43. As a result, the lens 93 and the imaging element 33 aresubjected to direct adhesion and fixing by the adhesive resin 37. Inother words, the lens 93 and the imaging element 33 are attached via theadhesive resin 37. The adhesive resin 37 is, for example, a type ofadhesive that allows curing to proceed up to a certain level of hardnessby ultraviolet irradiation although it requires heat treatment to obtaina final hardness.

The lens 93 and the element cover glass 43 are attached via the adhesiveresin 37 in the endoscope 11 according to the present embodiment. As aresult, the adhesive resin 37 in the endoscope 11 has a substantiallylinear shape in a side view (refer to FIG. 5). FIG. 5 is a perspectiveview illustrating an appearance of the imaging element 33 of theendoscope 11 according to the present embodiment that is seen from arear side with the transmission cable 31 connected to the conductorconnection portions 49. In the endoscope 11 according to the presentembodiment, the lens 93 and the element cover glass 43 are attached inedge portions on both end sides of the lens 93 by the adhesive resin 37and the adhesive resin 37 is applied only to the edge portions.

The lens 93 is, for example, a single lens. The lens 93 is formed in theshape of a prism that has the same outer shape as the imaging element 33and has a square cross section in the direction perpendicular to thedirection of the axis through the optical axis or the lens center. Thelens 93 allows incident light from the subject that has passed throughthe objective cover glass 91 to be imaged on the imaging surface 41 ofthe imaging element 33 via the element cover glass 43. A recessedportion is formed on a surface of the lens 93 on the element cover glass43 side. A convex surface portion 97 bulging in a substantiallyspherical shape is formed on a bottom surface of the recessed portion.With the convex surface portion 97, the lens 93 functions as an opticalelement performing light focusing. A bulging tip of the convex surfaceportion 97 is slightly separated from the element cover glass 43.Quadrangular ring-shaped end faces of the lens 93 that surround therecessed portion adhere to the element cover glass 43 via the adhesiveresin 37. As a result, a state is achieved where the recessed portionbetween the lens 93 and the element cover glass 43 is sealed with airinside. It is preferable that the air inside the sealed recessed portionthat has become a sealed space is dry air. In addition, the recessedportion may be sealed with nitrogen inside. In this manner, the airlayer 95 that has the recessed portion as its internal volume is formedbetween the lens 93 and the element cover glass 43. The convex surfaceportion 97 is placed in the air layer 95. In other words, alight-emitting surface of the convex surface portion 97 is in contactwith the air in the lens 93.

Whether the number of lenses can be reduced or not is an importantrequirement for diameter reduction for the endoscope 11 with the maximumouter diameter Dmax of 1.0 mm. Accordingly, important in a case wherethe lens 93 that is the single lens is disposed in the endoscope 11 ishow to make a refractive index difference with respect to the lens in atiny region in a width direction parallel to the optical axis direction.The endoscope 11 according to the third configuration example ischaracterized by the air layer with which a large refractive indexdifference is obtained with respect to the lens 93 being disposed on theoptical element surface.

In the endoscope 11 according to the third configuration example, therecessed portion is formed in the lens 93, the convex surface portion 97is formed on the bottom surface of the recessed portion, and thequadrangular ring-shaped end faces adhere to the element cover glass 43as described above. Accordingly, the air layer 95 for an increase inrefractive index difference with respect to the lens 93 can be ensuredin the tiny region. In addition, optical axis alignment between the lens93 and the imaging surface 41 can be performed with ease. The lens 93 iscapable of ensuring the air layer 95, and thus a high level of lenspower can be obtained with respect to the lens 93. Accordingly, thenumber of lenses in the endoscope 11 can be reduced to one. As a result,size and cost reduction for the endoscope 11 can be achieved.

Fourth Configuration Example

In the endoscope 11 according to the present embodiment, the endoscope11 according to the fourth configuration example is provided with a moldportion 65 and a tubular sheath 61 as illustrated in FIG. 3. The moldportion 65 fixes an outer peripheral surface of the objective coverglass 91 excluding its objective surface, an outer peripheral surface ofthe lens 93, and the imaging element 33 by coating with the mold resin17, forms an outer shell of the tip portion 15, and is exposed to theoutside. The sheath 61 is formed to have the same outer diameter as thetip portion 15 and is connected to the mold portion 65 by covering atleast a part of the mold portion 65.

The sheath 61 is formed of a resin material that has flexibility. Thesheath 61 can be provided with a single wire, a plurality of wires, anda braided tensile strength wire on its inner peripheral side so thatstrength is given. Examples of the tensile strength wire can include anaramid fiber such as a poly-p-phenylene terephthalamide fiber, apolyester fiber such as a polyarylate fiber, a polyparaphenylenebenzbisoxazole fiber, and a polyethylene terephthalate fiber, a nylonfiber, a thin tungsten wire, and a thin stainless steel wire. The sheath61 is formed of the flexible resin material as described above. Inaddition, the sheath 61 can be provided with the single wire, theplurality of wires, and the braided tensile strength wire on its innerperipheral side so that the strength is given as described above. Thematerial of the tensile strength wire is as described above.

In the endoscope 11, the objective cover glass 91, the lens 93, theelement cover glass 43, the imaging element 33 as a whole, a part of thetransmission cable 31, and a part of the light guide 57 are coated withthe mold resin 17 and fixed with the mold resin 17 exposed to theoutside. A radiopaque marker may be included in the tip portion 15 ofthe endoscope 11. This allows confirmation of the tip position of theendoscope 11 to be facilitated under X-ray fluoroscopy.

The lighting member is disposed along the objective cover glass 91, thelens 93, the element cover glass 43, and the imaging element 33 in theendoscope 11. In other words, the endoscope 11 according to the fourthconfiguration example has the light guide 57 as an example of thelighting member. This case where the lighting member is the light guide57 will be described as an example below. Still, the lighting member canalso be an LED attached to an insertion tip surface of the tip portion15. In this case, the light guide 57 is unnecessary.

The light guide 57 is made up of a single strand of optical fiber 59. Aplastic optical fiber (POF) or the like is preferably used as theoptical fiber 59. Both the core and cladding of the plastic opticalfiber are formed from plastic with a silicone resin and an acrylic resinused as its materials. The optical fiber 59 may also be, for example, abundle fiber in which a plurality of optical fiber strands is bundled upwith terminal fittings attached to both of its ends. A tip of theoptical fiber 59 is an emission end face in the tip portion 15 and abase end of the optical fiber 59 is connected to a ferrule of the plugportion 23. A light source is an LED disposed in, for example, thesocket portion 27. The plug portion 23 is connected to the socketportion 27 in the endoscope 11, and thus light from the LED propagatesthrough the optical fiber 59 of the light guide 57 and is emitted fromthe tip. According to this configuration, the single strand of opticalfiber can constitute the path reaching an illumination light emissionend from the light source, and thus optical loss reduction can beachieved.

The endoscope 11 according to the fourth configuration example isprovided with the light guide 57 as described above, and thus imaging ina dark portion can be conducted with the endoscope 11 alone.

As illustrated in FIG. 2, the endoscope 11 according to the fourthconfiguration example has a configuration in which the plurality oflight guides 57 as an example of the lighting member is respectivelydisposed around the objective cover glass 91, the lens 93, the elementcover glass 43, and the imaging element 33. For example, the four lightguides 57 can be disposed at equal intervals and in a uniform manner.Since the four light guides 57 are respectively disposed at the equalintervals and in the uniform manner as described above around theobjective cover glass 91, the lens 93, the element cover glass 43, andthe imaging element 33, the endoscope 11 according to the fourthconfiguration example is unlikely to create a shade above, below, to theleft of, and to the right of the subject. Accordingly, the endoscope 11is capable of obtaining a clearer captured image than in a configurationin which the number of the light guides 57 is one and a configuration inwhich the number of the light guides 57 is two.

The imaging element 33 is formed to have the square shape in theendoscope 11 according to the present embodiment. The optical fibers 59of the four light guides 57 are arranged substantially at the centers ofrespective side portions of the substrate of the imaging element 33 in aspace that is sandwiched by the substrate of the imaging element 33 andthe circle circumscribed about the substrate of the imaging element 33.

In the endoscope 11 according to the fourth configuration exampledescribed above, the space that is sandwiched by the square imagingelement 33 and the circular mold portion 65 substantially circumscribedabout the imaging element 33 can be effectively used, and thus theplurality of (four, in particular) optical fibers 59 can be easilyarranged without an increase in the outer diameter of the tip portion15. Accordingly, the endoscope 11 can be manufactured with ease and aclear image can be obtained from it without an increase in the outerdiameter of the tip portion 15.

In the endoscope 11, the objective cover glass 91, the lens 93, theelement cover glass 43, the imaging element 33, the part of thetransmission cable 31, and the part (imaging unit) of the light guide 57are coated with the mold resin 17 and fixed, and thus few componentsintervene during the fixing of each of these members. Accordingly, thediameter of the tip portion 15 of the endoscope 11 can be reduced, and aminimum-dimension configuration is available in a case where furtherdiameter reduction is pursued. Component costs can be reduced as well.For example, the endoscope 11 can be realized to be capable of beingapplied such that imaging can be performed on affected areas withextremely small diameters such as the blood vessels in the human body.As a result, size and cost reduction for the endoscope 11 can beachieved.

The mold resin 17 is molded to cover the section that reaches theobjective cover glass 91 from the imaging element 33, and thuscontributes to an increase in the fixing strength of these imagingunits. The mold resin 17 adds to the airtightness (that is, the absenceof very small gaps), watertightness, and light-shielding property of theair layer 95 as well. The mold resin 17 adds to the light-shieldingproperty at a time when the optical fiber 59 for the light guide 57 isembedded, too.

The light guide 57 is molded by the mold resin 17 in the tip portion 15of the endoscope 11, and thus the connection strength between the softportion 29 and the tip portion 15 can be improved even in thesmall-diameter endoscope 11 with the light guide 57 allowed to act as astructural material. In the endoscope 11, the coating with the moldresin 17 covers the objective cover glass 91 of the tip portion 15 andthe four optical fibers 59 in a case where the tip portion 15 is seenfrom an insertion side outermost surface (refer to FIG. 2, for example),and thus no clearance exists around (that is, no gap exists around) eachof the objective cover glass 91 and the four optical fibers 59.Accordingly, once the endoscope 11 is sterilized (that is, washed) afterbeing used during an inspection or surgery, unnecessary adhesion ofresidue from the washing, such as a liquid, to the endoscope 11 ismitigated and much more convenience in terms of hygiene can be providedwith regard to the use of the endoscope 11 during the next inspection orsurgery.

Axes of tip portions and optical axes of lens units are eccentric insome of existing endoscopes. In this type of configuration, the distanceto a subject is likely to vary with the rotation angle of the tipportion and stable acquisition of an acceptable image is unlikely. Inaddition, when the axis of the tip portion and the optical axis of thelens unit are eccentric, the degree of interference between a pipe innerwall and the tip portion varies with the rotation angle of the tipportion and operability is reduced during a movement into a hole with asmall diameter in particular. In the endoscope 11, in contrast, theobjective cover glass 91, the lens 93, the element cover glass 43, andthe imaging element 33 are coaxially connected. In other words, theobjective cover glass 91 is placed concentrically with respect to thetip portion 15. As a result, the endoscope 11 according to the fourthconfiguration example facilitates diameter reduction, allows anacceptable image to be obtained in a stable way, and is capable ofadding to insertion operability.

Fifth Configuration Example

It is preferable that the thickness of the sheath 61 ranges from 0.1 to0.3 mm in the endoscope 11 according to the fifth configuration example.

The mold portion 65 of the endoscope 11 has a small-diameter extendingportion 71 that is illustrated in FIG. 3 and extends backwards from arear end covering the imaging element 33. The small-diameter extendingportion 71 is molded in the form of a cylinder and the four opticalfibers 59 are embedded therein. The transmission cable 31 is embeddedinside the four optical fibers 59 in the small-diameter extendingportion 71. An inner diameter side of the sheath 61 is fixed to an outerperiphery of the small-diameter extending portion 71 by an adhesive orthe like. In other words, the mold portion 65 and the sheath 61 lead toeach other with a coaxial maximum outer diameter Dmax of 1.0 mm.

In the endoscope 11 according to the fifth configuration exampledescribed above, the thickness of the sheath 61 can be increased up to0.3 mm, and thus the tensile strength of the sheath 61 can be increasedwith ease. The transmission cable 31 has a minimum outer diameter ofapproximately 0.54 mm at this moment. The thickness of the sheath 61becomes 0.23 mm in a case where the maximum outer diameter Dmax of thetip portion 15 becomes 1.0 mm. In this manner, the maximum outerdiameter Dmax of the tip portion 15 can become 1.0 mm in the endoscope11 by the thickness of the sheath 61 being within the range of 0.1 to0.3 mm described above.

Sixth Configuration Example

The sixth configuration example shows a configuration example of thelens shape as a specific example of the configuration of the lens 93 inthe endoscope 11. FIGS. 6 to 8 are drawings illustrating a first exampleof the lens shape in the endoscope 11 according to the presentembodiment.

A single lens constitutes a lens 93A according to the first example. Inthis single lens, a first surface LR1 on the subject side is a flatsurface and a second surface LR2 on an imaging side is a convex surface.An optical element portion 201 is formed in a middle portion of theimaging side of the lens 93A, the optical element portion 201 has theconvex surface portion 97 constituting the lens surface of the convexsecond surface LR2, bulging in a substantially spherical shape, andhaving the shape of a circular dome, and an edge portion 202 isintegrally formed in a peripheral edge portion as a frame that has anadhesion surface 203 which has a flat end face. The edge portion 202 islarger in thickness-direction (optical axis-direction) dimension than acentral portion of the convex surface portion 97 of the optical elementportion 201, is shaped such that the adhesion surface 203 of the edgeportion 202 protrudes more than the convex surface portion 97, and is apart that is fixed to the element cover glass 43 by the adhesive resin37 adhering to the entire region of the adhesion surface 203. Theadhesion surface 203 of the edge portion 202 has a substantially squareshape, in which an outer peripheral portion has a square shape and aninner peripheral portion has a rounded square shape, and its four sidesexcluding corner portions have substantially the same width. An adhesionwidth Wa at the parts of the adhesion surface 203 of the edge portion202 where the four sides have the same width is, for example, at least50 μm. Inside the edge portion 202, the air layer 95 is formed betweenthe convex surface portion 97 as the lens surface of the second surfaceLR2 and the element cover glass 43.

The lens 93 has a thickness-direction dimension (thickness SRt) of, forexample, 100 μm to 500 μm. In the illustrated example, the edge portion202 has a thickness TE of 200 μm and a thickness TL between the firstsurface LR1 and an outer peripheral portion of the convex surfaceportion 97 (second surface LR2) of the optical element portion 201 is110 μm to 120 μm. An inclined surface 204, which widen from the lenscenter toward the outer periphery, ranges from the outer peripheralportion of the convex surface portion 97 of the optical element portion201 to the inner peripheral portion of the adhesion surface 203 of theedge portion 202. The inclined surface 204 has an angle πA of, forexample, 60° assuming that the angle θA is an angle of an opening seenfrom the lens center.

FIGS. 9 to 11 are drawings illustrating a second example of the lensshape in the endoscope 11 according to the present embodiment. In a lens93B according to the second example, the optical element portion 201 isformed in the middle portion of the imaging side of the lens 93B, theoptical element portion 201 has the convex surface portion 97constituting the lens surface of the convex second surface LR2, bulgingin a substantially spherical shape, and having the shape of a circulardome, and the edge portion 202 is integrally formed in the peripheraledge portion as the frame that has the adhesion surface 203 which hasthe flat end face. The following description will focus on theconfiguration of the parts that differ from those of the first exampleand description of the parts that are similar to those of the firstexample will be omitted. The adhesion surface 203 of the edge portion202 has the shape of a circle concentric with respect to the convexsurface portion 97, in which the outer peripheral portion has a squareshape and the inner peripheral portion has a circular dome shape, andthe adhesion width Wa of the minimal part is, for example, 50 μm. A flatportion 205 that is formed in the outer peripheral portion of the convexsurface portion 97 (second surface LR2) of the optical element portion201 has a width We of, for example, 13 μm. The inclined surface 204,which widens from the lens center toward the outer periphery, rangesfrom the flat portion 205 in the outer peripheral portion of the opticalelement portion 201 to the inner peripheral portion of the adhesionsurface 203 of the edge portion 202. The angle θA of the inclinedsurface 204 is, for example, 60° assuming that the angle θA is the angleof the opening seen from the lens center.

FIGS. 12 to 15 are drawings illustrating a third example of the lensshape in the endoscope 11 according to the present embodiment. In a lens93C according to the third example, the optical element portion 201 isformed in the middle portion of the imaging side of the lens 93C, theoptical element portion 201 has the convex surface portion constitutingthe lens surface of the convex second surface LR2, bulging in asubstantially spherical shape, and having the shape of a circular dome,and the edge portion 202 is integrally formed in the peripheral edgeportion as the frame that has the adhesion surface 203 which has theflat end face. The following description will focus on the configurationof the parts that differ from those of the first example and descriptionof the parts that are similar to those of the first example will beomitted. The optical element portion 201 in the middle portion has theshape of a mold in which four parts 206 on the circumferencecorresponding to the four sides of the square shape that is the outershape of the lens are partially notched in the outer peripheral portionof the circular dome-shaped convex surface portion 97. The inclinedsurface 204 is formed in the edge portion 202 of the peripheral edgeportion and ranges from the inner peripheral portion of the adhesionsurface 203 to the outer peripheral portion of the optical elementportion 201 that has a barrel shape. As illustrated in FIG. 15, the lens93C according to the third example is shaped by unnecessary parts of animage circle 212 of the circular lens 93C, that is, four outer peripheryregions 214 into which beams imaged on a region 213 outside the foursides of an imaging surface 211 are incident, being cut with respect tothe imaging surface 211 of the imaging element 33 that has a squareshape. The angle θA of the inclined surface 204 in the inner peripheralportion of the edge portion 202 is, for example, 90° assuming that theangle θA is the angle of the opening seen from the lens center and theslope can be formed to be gentler than in the first example and thesecond example. When the angle θA of the inclined surface 204 in theinner peripheral portion of the edge portion 202 is 60° as in the firstexample and the second example, the adhesion width Wa of the adhesionsurface 203 of the edge portion 202 can be increased.

The lens 93 is fabricated by nanoimprint, injection molding, or thelike. The lens 93 is fabricated by a lens group in which a plurality oftiny lenses that has the same shape is arranged being formed by a moldbased on an original plate for the nanoimprint or the like being used,the lens group being released as a molded object, and then it being cutinto individual lenses by dicing or the like. A draft needs to beprovided during the fabrication of the lens 93 for the lens 93 to beremoved from the mold, and the inclined surface 204 of the lens 93 actsas the draft. The higher the level of the draft of the molded object,the better in terms of releasability. Accordingly, it is desirable interms of releasability that the inclined surface 204 of the lens 93 isgentle with respect to a surface perpendicular to the optical axis ofthe lens 93. For a decrease in the external dimension of the lens 93,the inclined surface 204 of the lens 93 should be upright to the maximumextent possible. In addition, it is preferable in terms of adhesivestrength that the adhesion surface 203 of the edge portion 202 to whichthe adhesive resin 37 adheres has the largest possible adhesion area ina case where the lens 93 is allowed to adhere to the element cover glass43 by the adhesive resin 37.

Accordingly, the dimension of the adhesion surface 203 of the edgeportion 202 is set by comprehensive consideration being given to each ofthe factors of the reduction of the diameter of the lens 93,releasability, and adhesive strength so that reliable adhesion can beconducted between the lens 93 and the element cover glass 43 in the edgeportion 202. The adhesion width Wa of the adhesion surface 203 of theedge portion 202 is, for example, at least 50 μm in a case where, forexample, 0.5 mm is the dimension of one side of the square shape of thecross section perpendicular to the optical axis direction or the axialdirection through the lens center as an example of the size of the lens93 with the external shape of a quadrangular prism. In this case, thedimension of one side of the outer shape of the lens 93 is 0.5 mm orless and the adhesion width Wa of at least 50 μm is ensured for theadhesion surface 203 in the edge portion 202 in the endoscope 11 inwhich the maximum outer diameter Dmax of the tip portion 15 is 1.0 mm orless. In addition, the angle θA of the inclined surface 204 ranges, forexample, from 60° to 90° assuming that the angle θA is the angle of theopening seen from the lens center so that a reduction in the size of thelens 93 and releasability can be achieved at the same time. In thiscase, the angle of the inclined surface 204 ranges from 30° to 45° withrespect to the optical axis direction of the lens 93 (direction parallelto the release direction) and ranges from 45° to 60° with respect to asurface perpendicular to the axial direction through the optical axis orthe lens center of the lens 93.

With the endoscope 11 according to the sixth configuration exampledescribed above, the small-diameter lens 93 can be realized in which themaximum outer diameter Dmax of the tip portion 15 can be 1.0 mm or less.In addition, a sufficient adhesion area between the lens 93 and theelement cover glass 43 can be ensured when the adhesion width Wa of theadhesion surface 203 of the edge portion 202 is at least 50 μm in thelens 93 with a reduced diameter, and thus reliable adhesion and fixingcan be conducted. Furthermore, releasability can be improved during lensfabrication when the angle θA of the opening seen from the lens centerranges from 60° to 90° as the angle of the inclined surface 204 betweenthe optical element portion 201 in the middle portion of the lens 93 andthe edge portion 202 in the peripheral edge portion.

Seventh Configuration Example

The seventh configuration example shows a configuration example of thesurface of the lens 93 adhering to the element cover glass 43 in theendoscope 11.

FIG. 16 is a diagram illustrating the configuration example of thesurface of the lens 93 of the endoscope 11 according to the presentembodiment that adheres to the element cover glass 43. The lens 93 isallowed to adhere by the adhesive resin 37 with its quadrangularprismatic external shape corresponding to the element cover glass 43 ofthe imaging element 33. In this manner, fixing can be conducted withoptical axis alignment between the imaging surface 41 of the imagingelement 33 and the element cover glass 43 performed with ease. Theadhesion surface 203 of the edge portion 202 of the lens 93 may alsohave an inclined portion 207 inclined to have a predetermined angle,instead of the flat surface parallel to the end face of the elementcover glass 43, in a state where it faces the element cover glass 43 foradhesion and fixing. The inclined portion 207 of the adhesion surface203 has a tapered shape and is inclined from the inner peripheralportion toward the outer peripheral portion of the edge portion 202 withthe thickness dimension of the outer peripheral portion very slightlyreduced. The inclined portion 207 of the adhesion surface 203 has aninclination angle of, for example, at least 0.5°. In a case where a verysmall amount of the adhesive resin 37 is applied to the adhesion surface203 of the edge portion 202 for adhesion between the lens 93 and theelement cover glass 43, the adhesive resin 37 on the adhesion surface islikely to move to the outer periphery side and is unlikely to move tothe inside of the edge portion 202 because of the inclined portion 207of the adhesion surface 203, and thus the adhesive resin 37 interferingwith the air layer 95 formed in the optical element portion 201 can beprevented.

In the endoscope 11 according to the seventh configuration exampledescribed above, penetration of the air layer 95 between the lens 93 andthe element cover glass 43 by the adhesive resin 37 can be prevented andreliable adhesion and fixing can be conducted between the lens 93 andthe element cover glass 43 with the air layer 95 ensured.

Eighth Configuration Example

The eighth configuration example shows a specific example of theconfiguration of an optical system in the endoscope 11.

The specific example of the configuration of the optical systemincluding the objective cover glass 91, the lens 93, and the elementcover glass 43 will be shown below.

Objective Cover Glass 91

Thickness TGt of objective cover glass 91: TGt=0.1 to 0.5 mm

Example of material of objective cover glass 91: BK7 (manufactured bySchott), nd=1.52, νd=64.2

Refractive index ndF of objective cover glass 91: 1.3≤ndF

Abbe number νdF of objective cover glass 91: 30≤νdF

Element Cover Glass 43

Thickness SGt of element cover glass 43: SGt=0.1 to 0.5 mm

Example of material of element cover glass 43: BK7 (manufactured bySchott), nd=1.52, νd=64.2

Refractive index ndR of element cover glass 43: 1.3≤ndR≤2.0, ndF≤ndR

Abbe number νdR of element cover glass 43: 40≤νdR, νdF≤νdR

Lens 93

Focal distance f of lens 93: 0.1 mm≤f≤1.0 mm

F number FNO of lens 93: 1.4≤FNO≤8.0

Ninth Configuration Example

The ninth configuration example shows a specific example of theconfiguration of the imaging element 33 in the endoscope 11. FIGS. 17and 18 are drawings illustrating a first example of the imaging element33 in the endoscope 11 according to the present embodiment.

An imaging element 33A according to the first example is formed suchthat it has a quadrangular sectional shape when cut by a planeperpendicular to the axial direction through the optical axis or thelens center of the lens 93. In this case, the imaging surface on anelement cover glass 43A side and the terminal surface on thetransmission cable side have a quadrangular outer shape and the imagingelement 33A and the element cover glass 43A are formed in the externalshape of a quadrangular prism. In addition, the imaging element 33A andthe element cover glass 43A are formed to have the same quadrangularprismatic external shape as the lens 93 (not illustrated).

An electric circuit 99A following a circuit pattern is disposed on asubstrate (terminal surface) disposed on a rear end side of the imagingelement 33A with the conductor connection portions (connection clamps)49 respectively disposed at the four corner portions and thetransmission cable 31 based on the four electric wires 45 connected bysoldering or the like. In other words, the four electric wires 45 areconnected to the four corner portions of the terminal surface of theimaging element 33A. The four electric wires 45 are positioned in andconnected to the four corner portions of the terminal surface of theimaging element 33A in a state where each of their end portions ismolded in a crank shape. The width (length of one side of thequadrangular section) SQL of the outer shape of the imaging element 33Ais, for example, 0.5 mm or less. The pitch PC between those of the fourelectric wires 45 that are next to each other is, for example, at least0.3 mm.

FIGS. 19 and 20 are drawings illustrating a second example of theimaging element 33 in the endoscope 11 according to the presentembodiment. An imaging element 33B according to the second example isformed such that it has an octagonal sectional shape when cut by theplane perpendicular to the axial direction through the optical axis orthe lens center of the lens 93 and the imaging element 33B and a elementcover glass 43B are formed to have the external shape of an octagonalprism. In addition, the imaging element 33B, the element cover glass43B, and an electric circuit 99B are formed to have the same octagonalprismatic external shape as the lens 93 (not illustrated). The followingdescription will focus on the configuration of the parts that differfrom those of the first example and description of the parts that aresimilar to those of the first example will be omitted.

The second example is an example that has an octagonal shape obtained byeach of the four corner portions (four corners) of the quadrangularsectional shape of the imaging element 33B being cut (chamfered) in theform of one cut surface 221B. When it comes to the dimension of the cutpart of the outer shape of the imaging element 33B, a dimension CS tothe end portion of the cut surface 221B with respect to the vertex ofthe quadrangular shape is, for example, 20 to 50 μm. When the fourcorner portions of the outer shape of the imaging element 33B are cut inthe form of the cut surface 221B as described above, the inter-electricwire pitch PC of the four electric wires 45 can be separated to themaximum extent possible and the external dimension of the imagingelement 33B in a diagonal direction can be reduced, which can contributeto further endoscope diameter reduction. When the dimension CS of thecut part is 21.2 μm, for example, the external dimension of the imagingelement 33B in the diagonal direction is reduced by 15 μm at one placeand the diameter is reduced by 30 μm in both ends in the diagonaldirection. When this configuration of the cut surface 221B is applied toan imaging element in which the external dimension SQL of one side is0.5 mm and the external dimension in the diagonal direction is 0.705 mmin a state where the external shape is a square shape, the externaldimension in the diagonal direction is reduced to 0.675 mm by thechamfering and a small-diameter endoscope in which φ is 0.7 mm or lesscan be realized.

FIGS. 21 and 22 are drawings illustrating a third example of the imagingelement 33 in the endoscope 11 according to the present embodiment. Animaging element 33C according to the third example is formed such thatit has a dodecagonal sectional shape when cut by the plane perpendicularto the axial direction through the optical axis or the lens center ofthe lens 93 and the imaging element 33C and a element cover glass 43Care formed to have the external shape of a dodecagonal prism. Inaddition, the imaging element 33C, the element cover glass 43C, and anelectric circuit 99C are formed to have the same octagonal prismaticexternal shape as the lens 93 (not illustrated). The followingdescription will focus on the configuration of the parts that differfrom those of the first example and description of the parts that aresimilar to those of the first example will be omitted. The third exampleis an example that has a dodecagonal shape obtained by each of the fourcorner portions of the quadrangular sectional shape of the imagingelement 33C being cut in the form of two cut surfaces 221C. When itcomes to the dimension of the cut part of the outer shape of the imagingelement 33C, the dimension CS to the end portion of the cut surface withrespect to the vertex of the quadrangular shape can exceed that of thesecond example because of the cutting with the two surfaces.Accordingly, the diameter of the imaging element can be further reduced.

The sectional shape in the direction perpendicular to the axialdirection through the lens optical axis or the lens center of theimaging element 33 is not limited to the quadrangular, octagonal, anddodecagonal shapes and may be a shape that has 4×n sides (n being anatural number) such as the shape of a hexadecagon. When the imagingelement 33 is configured to have a sectional shape that has the 4×nsides as described above, the diameters of the imaging element and theendoscope can be further reduced while the transmission cable 31 basedon the four electric wires 45 is allowed. When the four corners of thesectional shape of the imaging element 33 that has the 4×n sides have achamfered shape, the dimension of the imaging element 33 in the diagonaldirection can be further reduced, and then contribution can be made tofurther diameter reduction.

With the endoscope 11 according to the ninth configuration exampledescribed above, the small-diameter imaging element 33 can be realizedin which the maximum outer diameter Dmax of the tip portion 15 can be1.0 mm or less.

The endoscope 11 according to the present embodiment is provided withthe imaging element 33 disposed in the tip portion 15 of the insertionportion 21 with the imaging surface 41 covered by the element coverglass 43, the lens 93 that allows the incident light from the subject tobe imaged on the imaging surface 41, and the adhesive resin 37 fixingthe lens 93 and the element cover glass 43 to each other. The lens 93 isformed to have a prismatic external shape with the single lens in whichthe first surface on the subject side is the flat surface and the secondsurface on the imaging side is the convex surface constituting the lens93. The optical element portion 201 is formed in the middle portion ofthe imaging side of the lens 93, the optical element portion 201 has theconvex surface portion 97 constituting the convex lens surface andbulging in a substantially spherical shape, and the edge portion 202that has the adhesion surface 203 which has the flat end face isintegrally formed in the peripheral edge portion. In this manner, thesmall-diameter lens 93 can be realized in which the maximum outerdiameter Dmax of the tip portion 15 can be 1.0 mm or less.

In the endoscope 11 according to the present embodiment, the adhesionsurface 203 of the lens 93A has a substantially square shape in whichthe outer peripheral portion has a square shape and the inner peripheralportion has a rounded square shape.

In the endoscope 11 according to the present embodiment, the adhesionsurface 203 of the lens 93B has the shape of a circle concentric withrespect to the convex surface portion 97, in which the outer peripheralportion has a square shape and the inner peripheral portion has acircular dome shape.

In the endoscope 11 according to the present embodiment, the opticalelement portion 201 of the lens 93C has the shape of a mold in which thefour parts on the circumference corresponding to the four sides of thesquare shape that is the outer shape of the lens are partially notchedin the outer peripheral portion of the circular dome-shaped convexsurface portion 97. As a result, the inclined surface 204 between theoptical element portion 201 and the edge portion 202 can be formed tohave a gentle slope and releasability can be improved during lensfabrication. In a case where the slope of the inclined surface 204 isthe same, the adhesion width Wa of the adhesion surface 203 of the edgeportion 202 can be increased and adhesive strength can be improved.

In the endoscope 11 according to the present embodiment, the lens 93 hasthe inclined surface 204 that widens from the lens center toward theouter periphery and ranges from the outer peripheral portion of theconvex surface portion 97 to the inner peripheral portion of theadhesion surface 203, the angle of the inclined surface 204 ranges from60° to 90° assuming that it is the angle θA of the opening seen from thelens center, and the adhesion width Wa of the adhesion surface 203 is atleast 50 μm. Accordingly, reliable adhesion and fixing can be conductedbetween the lens 93 and the element cover glass 43 with the lens 93 thathas a reduced diameter. Since the angle of the inclined surface 204 canbe sufficiently ensured, releasability can be improved during lensfabrication.

In the endoscope 11 according to the present embodiment, the adhesionsurface 203 of the lens 93 has the tapered inclined portion 207 inclinedfrom the inner peripheral portion toward the outer peripheral portion ofthe edge portion 202. Accordingly, the adhesive resin 37 applied to theadhesion surface 203 is likely to move to the outer periphery side andis unlikely to move to the inside of the edge portion 202, and thus theadhesive resin 37 interfering with the air layer 95 formed in theoptical element portion 201 can be prevented.

The endoscope 11 according to the present embodiment is provided withthe objective cover glass 91, which covers the surface of the lens 93 onthe subject side, as well as the imaging element 33, the element coverglass 43, the adhesive resin 37, and the lens 93. When it comes to anoptical material that constitutes the objective cover glass 91, thethickness TGt satisfies 0.1 mm≤TGt≤0.5 mm, the refractive index ndFsatisfies 1.3≤ndF, and the Abbe number νdF satisfies 30≤νdF. When itcomes to an optical material that constitutes the element cover glass43, the thickness SGt satisfies 0.1 mm≤SGt≤0.5 mm, the refractive indexndR satisfies 1.3≤ndR≤2.0 and ndF≤ndR, and the Abbe number νdR satisfies40≤νdR and νdF≤νdR. When it comes to the lens 93 based on the singlelens, the focal distance f satisfies 0.1 mm≤f≤1.0 mm and the F numberFNO satisfies 1.4≤FNO≤8.0. In this manner, the small-diameter lens 93can be realized in which the maximum outer diameter Dmax of the tipportion 15 can be 1.0 mm or less.

When the distance from an imaging point on the imaging side in the focaldistance of the lens 93 to the subject side end face of the elementcover glass 43 is x (0≤x≤f), the maximum angle of the beam emitted tothe imaging point from the lens 93 in an air-only state with respect tothe optical axis is θair, and the maximum angle of the beam emitted tothe imaging point from the lens 93 in a state including the elementcover glass 43 through the element cover glass 43 with respect to theoptical axis is θgl in the endoscope 11 according to the presentembodiment, the lens 93 and the element cover glass 43 is based on acombination of the focal distance f, the F number FNO, and therefractive index ndR satisfying 0.1≤x·(tan θair)/(tan θgl)≤0.5. As aresult, a desired optical performance can be obtained from thesmall-diameter lens 93.

The endoscope 11 according to the present embodiment is provided withthe transmission cable 31 that has the four electric wires 45 which arerespectively connected to the four conductor connection portions 49disposed on the surface of the imaging element 33 on the side oppositeto the imaging surface 41 as well as the imaging element 33, the elementcover glass 43, the adhesive resin 37, and the lens 93. The imagingelement 33 has a sectional shape that has the 4×n sides (n being anatural number) in the direction perpendicular to the axial directionthrough the optical axis or the lens center of the lens 93 and the fourelectric wires 45 are respectively connected to the four conductorconnection portions 49 placed at the four corners of the rear end faceof the imaging element 33 which has the 4×n sides. As a result, thesmall-diameter imaging element 33 can be realized in which the maximumouter diameter Dmax of the tip portion 15 can be 1.0 mm or less.

In the endoscope 11 according to the present embodiment, the fourcorners of the sectional shape of the imaging element 33 that has the4×n sides have a chamfered shape. As a result, the dimension of theimaging element 33 in the diagonal direction can be further reduced andcontribution can be made to further diameter reduction.

In the endoscope 11 according to the present embodiment, the imagingelement 33 and the element cover glass 43 have the same prismaticexternal shape that has the 4×n sides as the lens 93. As a result, theouter diameter reaching the imaging element 33 through the element coverglass 43 from the lens 93 can be further reduced.

The length of one side of the cross section of the imaging element 33 inthe endoscope 11 according to the present embodiment that has the 4×nsides is 0.5 mm or less in the direction perpendicular to the axialdirection through the optical axis or the lens center. As a result, theexternal dimension of the imaging element 33 in the diagonal directioncan be reduced to approximately 0.7 mm.

In the endoscope 11 according to the present embodiment, the tip portion15 is formed to have a maximum outer diameter ranging from the finitediameter to 1.0 mm, which is equivalent to the diameter of the circlecircumscribed about the substrate of the imaging element 33. As aresult, the maximum outer diameter Dmax can be less than 1.0 mm, andthus insertion into the blood vessels in the human body can be furtherfacilitated.

Tenth Configuration Example

FIG. 23 is an enlarged perspective view of a main part, in which alight-shielding member of the endoscope 11 according to the presentembodiment is a notched holder. FIG. 24 is a plan sectional view of theendoscope 11 illustrated in FIG. 23. FIG. 25 is an exploded perspectiveview of the endoscope 11 illustrated in FIG. 23.

The endoscope 11 according to the tenth configuration example isprovided with a single lens (such as the lens 93) that has aquadrangular outer shape (such as a square shape and a rectangularshape) in the direction perpendicular to the optical axis or the lenscenter, the sheath 61 placed coaxially with respect to the optical axisor the lens center and surrounding the lens 93 with the surroundingouter periphery having a circular shape, the lighting member (such asthe light guide 57) placed between the outer periphery of the sheath 61and at least one side of the lens 93 and extending along the opticalaxis or the lens center, and the light-shielding member (such as acylinder holder 131) disposed between the lens 93 and the light guide57. The endoscope 11 further includes the imaging element 33 that has aquadrangular outer shape (such as a square shape and a rectangularshape) in the direction perpendicular to the optical axis or the lenscenter with the length of its one side being equal to the length of oneside of the lens and the element cover glass 43 covering the imagingsurface 41 of the imaging element 33 and having the same outer shape asthe imaging element 33 in the direction perpendicular to the opticalaxis or the lens center.

This endoscope 11 is assembled as follows. Specifically, a camera Assy(that is, a unit made up of a plurality of components related to acamera, the same applies hereinafter) is completed by assembly of thelens 93, the imaging element 33, and the transmission cable 31illustrated in FIG. 25. Then, a fiber Assy (that is, a unit made up of aplurality of components related to the optical fiber 59, the sameapplies hereinafter) is assembled. The fiber Assy is made up of, forexample, the plurality of light guides 57 and the cylinder holder 131 asan example of the light-shielding member. Then, the camera Assy and thefiber Assy are fixed by insertion into an opening portion at the centerof a housing of the cylinder holder 131 that is the fiber Assy. Adistance of approximately 50 (μm) or more is ensured between one side ofthe objective cover glass 91 and a notch 133. Finally, the cylinderholder 131 is wrapped with the sheath 61 and the sheath 61 is fixedwithout a gap by the adhesive resin 37.

In the endoscope 11 according to the tenth configuration example, thelight guide 57 is placed between the sheath 61 that has the circularouter periphery and at least one side of the quadrangular lens 93. As aresult, that space that is attributable to the shape difference betweenthe circular part of the sheath 61 and the quadrangular part of the lens93 can be used for the placement of the light guide 57 and memberplacement density in the tip portion 15 can be increased. In otherwords, space efficiency can be improved compared to existingconfigurations in which the light guide 57 is placed on the outerperiphery of a circular lens. As a result, a useless space can besuppressed and size reduction can be facilitated. Since the lens 93 andthe imaging element 33 have a quadrangular shape in the endoscope 11,alignment between the lens center and the imaging center can beperformed with ease. In addition, the four sides of the lens 93 and thefour sides of the imaging element 33 can be fixed to each other by theadhesive resin 37 and the four corners of the lens 93 and the imagingelement 33 can be fixed to each other by the adhesive resin 37, and thusan increase in fixing area can be achieved. As a result, the lens 93 andthe imaging element 33 can be fixed with a high level of strength.

In the endoscope 11 according to the tenth configuration example, theimaging element 33 has a quadrangular outer shape. The sheath 61 has acircular outer shape. In a case where the inner diameter of the sheath61 is allowed to approach the corner portion of the quadrangular imagingelement 33 to the maximum extent allowed by strength, the area that canbe used in the sheath becomes the space other than the space where thequadrangular imaging element 33 that is positioned at the center isplaced. This residual space is made up of four arcs and a half-mooncolumnar-shaped portion connecting both ends of this arc with onequadrangular side (straight line slightly longer than the one side to bespecific). In the endoscope 11, the light-shielding member (cylinderholder 131) is formed as a square hole tube in which the four half-mooncolumnar-shaped portions are respectively connected in the thin portionoutside the corner portion of the imaging element 33. In other words,the cylinder holder 131 of the endoscope 11 is formed by the residualspace other than the essential space being made the most of. As aresult, size reduction can be realized while light leaking from theextension-direction outside surface of the optical fiber 59 is reliablyblocked. This cylinder holder 131 can be a metallic holder (made from,for example, a SUS material).

The maximum outer diameter of the endoscope 11 illustrated in FIG. 23being 1.0 mm or less will be described in detail below with reference toFIG. 23. In FIG. 23, the shortest distance between the inner peripheralsurface of the sheath 61 and the four corners (corner portions) of theobjective cover glass 91 that has a quadrangular outer shape (such as asquare shape) in the direction perpendicular to the lens center isapproximately 50 μm in view of the manufacturability (including processability) and handling property (that is, being unlikely to be brokenduring assembly) of the endoscope 11. In addition, the length of oneside of each of the objective cover glass 91, the lens 93, the elementcover glass 43, and the imaging element 33 that has a quadrangular outershape (such as a square shape) in the direction perpendicular to thelens center is 500 μm, and thus its diagonal dimension is approximately705 μm. In addition, the thickness of the sheath 61 currently used is 97(μm) and the maximum outer diameter Dmax of the endoscope 11 is 705(μm)+50 (μm)+50 (μm)+97 (μm)≅1,000 (μm)=1.0 (mm), which is 1.0 (mm) orless.

Because the notch 133 is disposed in the thick half-moon columnar-shapedportion or a through-hole is drilled in this cylinder holder 131, theinsertion space of the light guide 57 can be easily ensured with littledecrease in the strength of the holder. In other words, it can be saidthat the shape is extremely high in terms of space efficiency. When thenotch 133 is formed in a rectangular shape in which a long side is alongone side in this case, the light guide can be efficiently placed andassemblability can be improved.

In the endoscope 11 according to the tenth configuration example, thecylinder holder 131 is longer than the length between the imagingsurface 41 of the imaging element 33 and an insertion tip surface 135 ofthe endoscope 11 in the tip portion 15.

In the endoscope 11 according to the tenth configuration example, thecylinder holder 131 shields the lens side surface of the lens 93 byextending more backwards than the imaging surface 41, and thuspenetration of a medium from the lens side surface by leaking light fromthe extension-direction outside surface of the optical fiber 59 can bereliably prevented.

In the endoscope 11 according to the tenth configuration example, thenotch 133 is formed in the cylinder holder 131. When the notch 133 isformed in the rectangular shape in which the long side is along one sideof the imaging element 33, the plurality of optical fibers 59 can beefficiently placed and processing can be facilitated. In a case wherethe optical fiber 59 has an outer diameter of 0.052 mm in the endoscope11 according to the tenth configuration example, for example, six on oneside, that is, 12 on both sides, can be accommodated at least in thedirection along the chord of the half-moon columnar-shaped portion. Therequired number may vary with the object of observation, the distance tothe object of observation, and the light source that is used.

In the endoscope 11 according to the tenth configuration example, theplurality of light guides 57 is placed substantially in point symmetrywith respect to the lens center.

The light guides 57 are placed in point symmetry with respect to thelens center of the lens 93 in this endoscope 11, and thus illuminationlight can be distributed upward, downward, leftward, and rightward in auniform manner when the circular inner peripheral surface is illuminatedwith the illumination light in particular. As a result, a shadow isunlikely to be created from the subject and the captured image becomesmore likely to be seen. Since the light guide 57 is in point symmetrywith respect to the axis of the tip portion 15, distribution of theillumination light is unlikely to change depending on the rotation angleof the tip portion 15 as well, and operability is improved during amovement into the blood vessel with a small diameter or the like inparticular.

In the endoscope 11 according to the tenth configuration example, theplurality of optical fibers 59 is placed in parallel to the lens sidesurface along the lens center of the lens 93 and is arranged in a rowalong one side of the lens 93.

In this endoscope 11, the optical fiber 59 can be vertically placedalong one side of the lens 93. As a result of this configuration,effective space utilization 59 can be conducted compared to placement ofthe optical fiber only at the center of one side. In addition, a widerange of the illumination light can be distributed in a uniform mannerby the endoscope 11 because the plurality of optical fibers 59 isarranged in a row along one side.

In the cylinder holder 131, a square tube connecting portion 137 forensuring the thickness of the sheath 61 may also be disposed to extendin a rear portion on the side opposite to the insertion tip surface 135.By the square tube connecting portion 137 being disposed, the cylinderholder 131 is capable of increasing the connection strength of thesheath 61. In other words, the sheath 61 can be thickened with theextrapolated part of the square tube connecting portion 137. Inaddition, it is preferable in terms of space efficiency improvement thata square hole 139 for accommodating the objective cover glass 91 that isdrilled in the cylinder holder 131 is formed by being allowed toapproach a cylinder outer peripheral circle to the maximum extentallowed by strength.

Accordingly, the space efficiency (member placement density) of theinsertion tip surface 135 can be increased (suppression of uselessspace) in the endoscope 11 according to the tenth configuration example,and thus size reduction can be achieved, the lens 93 and the imagingelement 33 can be easily fixed with a high level of strength, and straylight from the light guide 57 can be prevented as well.

In the insertion tip surface 135 of the endoscope 11, the space betweenthe sheath 61 and the camera Assy and the fiber Assy is filled without agap with the adhesive resin 37, and thus penetration of the tip portion15 by a liquid can be prevented and washing can be facilitated.

Eleventh Configuration Example

FIG. 26 is an enlarged perspective view of the main part, in which thelight-shielding member of the endoscope 11 according to the presentembodiment is a through-holed holder. FIG. 27 is an exploded perspectiveview of the endoscope 11 illustrated in FIG. 26.

The light-shielding member in the endoscope 11 according to the eleventhconfiguration example is a cylinder holder 141 that coaxiallyaccommodates the lens 93 and a through-hole 143 in a direction along thelens center is formed between one side of the lens 93 and the holderouter peripheral surface of the cylinder holder 141. The plurality ofoptical fibers 59 is inserted into the through-hole 143. In a case wherethe optical fiber 59 has an outer diameter of 0.052 mm in the endoscope11 according to the eleventh configuration example, for example, six onone side, that is, 12 on both sides, can be accommodated at least in thedirection along the chord of the through-hole 143. The required numbermay vary with the object of observation, the distance to the object ofobservation, and the light source that is used.

This endoscope 11 is assembled as follows. Specifically, a camera Assyis completed by assembly of the lens 93, the imaging element 33, and thetransmission cable 31 illustrated in FIG. 27. Then, a fiber Assy isassembled by the plurality of light guides 57 being attached to thecylinder holder 141. The fiber Assy is made up of, for example, theplurality of light guides 57 and the cylinder holder 141 as an exampleof the light-shielding member. The plurality of light guides 57 isinserted into and fixed to the through-hole 143 of the cylinder holder141. Then, the camera Assy is mounted on the cylinder holder 141 of thefiber Assy. Likewise, a distance of approximately 50 (μm) or more isensured between one side of the objective cover glass 91 and thethrough-hole 143. Finally, the cylinder holder 141 is wrapped with thesheath 61 and the gaps between the sheath 61 and the camera Assy and thefiber Assy are filled with the adhesive resin 37 to be fixed.

In the endoscope 11 according to the eleventh configuration example, thethrough-hole 143 in the direction along the lens center is formed in thehalf-moon columnar-shaped portion in the cylinder holder 141 as a squarehole tube. The through-hole 143 is a hole that has a substantiallyhalf-moon shape with the chord in the direction along one side, and thusthe light guide 57 can be efficiently placed.

The gaps (including the through-holes 143) that are attributable to thefixing of the camera Assy and the fiber Assy in the insertion tipsurface of the endoscope 11 are filled with the adhesive resin 37, andthus penetration of the tip portion 15 by a liquid can be prevented andwashing can be facilitated.

Twelfth Configuration Example

FIG. 28 is an enlarged perspective view of the main part, in which thelight-shielding member of the endoscope 11 according to the presentembodiment is a mold resin. FIG. 29 is a plan sectional view of theendoscope 11 illustrated in FIG. 28. FIG. 30 is an exploded perspectiveview of the endoscope 11 illustrated in FIG. 28.

The light-shielding member in the endoscope 11 according to the twelfthconfiguration example is a mold resin 145 that covers theextension-direction outside surface of the light guide 57.

This endoscope 11 is assembled as follows. Specifically, a camera Assyis completed by assembly of the lens 93, the imaging element 33, and thetransmission cable 31 illustrated in FIG. 30. Then, a fiber Assy iscompleted by resin molding. Then, the fiber Assy is fixed to the cameraAssy (refer to the dotted line). Finally, the fiber Assy to which thecamera Assy fixed is covered with the sheath 61 from its outside and thegaps between the fiber Assy and the camera Assy and the sheath 61 arefilled with a mold resin 146, which results in fixing without a gap.

In the endoscope 11 according to the twelfth configuration example, theplurality of optical fibers 59 that constitutes the light guide 57 isallowed to form a fiber bundle by the mold resin 145. The plurality ofoptical fibers 59 is arranged in a row along one side of the lens 93. Ina case where the optical fiber 59 has an outer diameter of 0.052 mm inthe endoscope 11 according to the twelfth configuration example, forexample, eight on one side, that is, 16 on both sides, can beaccommodated at least in the direction along the chord. The mold resin145 is molded in the same shape as the half-moon columnar-shaped portionat the position of any one of the four half-moon columnar-shapedportions described above. Regarding the mold resin 145, molten resinfilling is performed by the resin mold being used with the optical fiber59 placed in a cavity already filled with molten resin. In this manner,the plurality of optical fibers 59 is integrally molded in the half-mooncolumnar-shaped portion in a state where the optical fibers 59 arearranged in a row and inserted.

In a case where it is feared that light will leak from theextension-direction outside surface of the optical fiber 59 due to adecrease in thickness, a carbon-containing resin (such as a carbonblack-containing resin) can be used for the mold resin 145. In addition,a vapor deposited metallic film or the like or a screen printing-basedon light-shielding film may be formed on the lens side surface. In thismanner, its light-shielding performance can be further enhanced despitethe light-shielding member being the mold resin 145. In the insertiontip surface of the endoscope 11, the space between the sheath 61 and thecamera Assy and the fiber Assy is filled without a gap with the moldresin 146, and thus penetration of the tip portion 15 by a liquid can beprevented and washing can be facilitated.

Thirteenth Configuration Example

FIG. 31 is an enlarged perspective view of the main part, in which thelight-shielding member of the endoscope 11 according to the presentembodiment is a pipe 147. FIG. 32 is a plan sectional view of theendoscope 11 illustrated in FIG. 31. FIG. 33 is an exploded perspectiveview of the endoscope 11 illustrated in FIG. 31.

In the endoscope 11 according to the thirteenth configuration example,the light-shielding member is the pipe 147 that is inserted into thelight guide 57.

This endoscope 11 is assembled as follows. Specifically, a camera Assyis completed by assembly of the lens 93, the imaging element 33, and thetransmission cable 31 illustrated in FIG. 33. Then, a fiber Assy isassembled by the optical fiber 59 being inserted into the pipe 147 andfixed without a gap by the adhesive resin 37. Then, the fiber Assy isfixed without a gap by the adhesive resin 37 to a facing side surface ofthe camera Assy. Finally, the outside of the fiber Assy fixed to thecamera Assy is covered by the sheath 61 inserted into the transmissioncable 31 and the gaps between the sheath 61 and the camera Assy and thefiber Assy are filled with the adhesive resin 37 to be fixed. Theadhesive resin 37 is not illustrated in FIG. 31. Still, the gaps betweenthe sheath 61 and the camera Assy and the fiber Assy are filled with theadhesive resin 37. Although the adhesive resin 37 is illustrated in FIG.32 as providing adhesion at least up to the terminal end face of theimaging element 33 (that is, the terminal end face of the pipe 147), therange of adhesion of the adhesive resin 37 is not limited to the rangeof up to the terminal end face of the imaging element 33. For example,the adhesive resin 37 may provide adhesion including parts of theconductor connection portion 49, the electric wire 45, and thetransmission cable 31 further on the rear end side than the terminal endface of the imaging element 33 (that is, the side opposite to theobjective side) in the sheath 61.

In the endoscope 11 according to the thirteenth configuration example,the plurality of optical fibers 59 that constitutes the light guide 57can be shielded by insertion into an oval hole 149 of the pipe 147. In acase where the optical fiber 59 has an outer diameter of 0.052 mm in theendoscope 11 according to the thirteenth configuration example, forexample, eight on one side, that is, 16 on both sides, can beaccommodated at least in the direction along the oval hole 149. The pipe147 is formed as an elongated cylinder. A Ni electroforming material orthe like can be used as a material of the pipe 147. A minor axis of theelongated cylinder substantially corresponds to the outer diameter ofthe optical fiber 59. Accordingly, the pipe 147 allows the plurality ofoptical fibers 59 to be arranged in a row in a major-axis direction andbundled up. It is preferable that the optical fiber 59 inserted into thepipe 147 is fixed by the adhesive resin 37 described above. This pipe147 is capable of having a surface in the direction along a long axisfixed to the lens side surface. Because the elongated and cylindricalpipe 147 is used as the light-shielding member, shielding and bundlingof the plurality of optical fibers 59 can be performed with ease,reliability, and a high level of strength. In the tip surface of theendoscope 11, the space between the sheath 61 and the camera Assy andthe fiber Assy is filled without a gap with the adhesive resin 37, andthus penetration of the tip portion 15 by a liquid can be prevented andwashing can be facilitated.

Fourteenth Configuration Example

FIG. 34 is an enlarged perspective view of the main part, in which thelight-shielding member of the endoscope according to the presentembodiment is a jacket 151. FIG. 35 is an enlarged perspective view ofthe optical fiber 59 covered by the jacket 151 in FIG. 34.

The endoscope 11 according to the fourteenth configuration example isprovided with a single lens (such as the lens 93) that has aquadrangular outer shape (such as a square shape and a rectangularshape) in the direction perpendicular to the optical axis or the lenscenter, the sheath 61 placed coaxially with respect to the optical axisor the lens center and surrounding the lens 93 with the surroundingouter periphery having a circular shape, the lighting member (such asthe light guide 57) placed between the outer periphery of the sheath 61and at least one side of the lens 93 and extending along the opticalaxis or the lens center, and the light-shielding member disposed betweenthe lens 93 and the light guide 57. The light-shielding member is thejacket 151 covering the extension-direction outside surface of the lightguide 57. The jacket 151 is disposed for each of the optical fibers 59constituting the light guide 57. The endoscope 11 according to thefourteenth configuration example further includes the imaging element 33that has a quadrangular outer shape (such as a square shape and arectangular shape) in the direction perpendicular to the optical axis orthe lens center with the length of its one side being equal to thelength of one side of the lens 93 and the element cover glass 43covering the imaging surface 41 of the imaging element 33 and having thesame outer shape as the imaging element 33 in the directionperpendicular to the optical axis or the lens center.

This endoscope 11 is assembled as follows. Specifically, a camera Assyis completed by assembly of the lens 93, the imaging element 33, and thetransmission cable 31 illustrated in FIG. 30. Then, a fiber Assyincluding the plurality of optical fibers 59 where the jackets 151 aredisposed is completed by resin molding. Then, the fiber Assy is fixed tothe camera Assy (refer to the dotted line). Finally, the fiber Assy towhich the camera Assy fixed is covered with the sheath 61 from itsoutside and the gaps between the fiber Assy and the camera Assy and thesheath 61 are filled with the mold resin 146, which results in fixingwithout a gap. The mold resin 146 in the gaps between the fiber Assy andthe camera Assy and the sheath 61 is not illustrated in FIG. 34. Still,the gaps between the fiber Assy and the camera Assy and the sheath 61are filled with the mold resin 146. Although the mold resins 145 and 146are illustrated in FIG. 34 as providing coating at least up to theterminal end face of the imaging element 33, the range of coating of themold resins 145 and 146 is not limited to the range up to the terminalend face of the imaging element 33. For example, the mold resins 145 and146 may provide coating and fixing including parts of the conductorconnection portion 49, the electric wire 45, and the transmission cable31 further on the rear end side than the terminal end face of theimaging element 33 (that is, the side opposite to the objective side) inthe sheath 61.

In the endoscope 11 according to the fourteenth configuration example,the extension-direction outside surface of each of the optical fiber 59s is covered by the cylindrical jacket 151. A highly light-shieldingmaterial is used for the jacket 151. Examples of the highlylight-shielding material can include a carbon-containing resin.

In general, quartz glass and resin are used for a core 153 and cladding155 of the optical fiber 59. The light condensing capability of theoptical fiber 59 increases and bonding with a light source becomeseasier as its maximum acceptance angle NA (numerical aperture: number ofopenings) increases. Still an increase in NA leads to an increase inoptical loss and light dispersion between the core 153 and the cladding155. Accordingly, an optimum NA value needs to be obtained. Since thejacket 151 is disposed on the optical fiber 59, light leaking thatarises in a case where the optimum NA value is set can be reliablyblocked with a simple structure.

Fifteenth Configuration Example

The endoscope according to the fifteenth configuration example (notillustrated) is provided with a single lens (such as the lens 93) thathas a quadrangular outer shape (such as a square shape and a rectangularshape) in the direction perpendicular to the optical axis or the lenscenter, a sheath (such as the sheath 61) placed coaxially with respectto the optical axis or the lens center and surrounding the lens with thesurrounding outer periphery having a circular shape, the lighting member(such as the light guide 57) placed between the outer periphery of thesheath and at least one side of the lens and extending along the opticalaxis or the lens center, and the light-shielding member disposed betweenthe lens and the light guide. The light-shielding member is alight-shielding film (not illustrated) formed on the lens side surfacealong the lens center of the lens. The endoscope 11 according to thefifteenth configuration example further includes the imaging element 33that has a quadrangular outer shape (such as a square shape and arectangular shape) in the direction perpendicular to the optical axis orthe lens center with the length of its one side being equal to thelength of one side of the lens 93 and the element cover glass 43covering the imaging surface 41 of the imaging element 33 and having thesame outer shape as the imaging element 33 in the directionperpendicular to the optical axis or the lens center. In the endoscope11 according to the fifteenth configuration example, leaking light fromthe light guide 57 may be blocked by member of an appropriatecombination with the configuration of the endoscope according to thetenth to fourteenth configuration examples between the sheath 61 and thelight guide 57 and between the sheath 61 and the objective cover glass91, the lens 93, the element cover glass 43, and the imaging element 33.

Since the light-shielding film is formed on the lens side surface in theendoscope 11 according to the fifteenth configuration example, incidenceof light leaking from the extension-direction outside surface of theoptical fiber placed in its vicinity toward the lens side surface isprevented. The light-shielding film can be formed by vacuum deposition.During the vacuum deposition, a film-forming material goes throughevaporation and sublimation in a vacuum and its particles are subjectedto adhesion and deposition. Examples of the film-forming material caninclude aluminum, chromium, and gold.

In the tenth to fourteenth configuration examples described above, themaximum outer diameter Dmax is 1 mm or less. The maximum outer diameterDmax of the endoscope 11 may be less than 2 mm (such as 1.8 mm) as well.One side of the imaging element 33 has a maximum length of 0.51 mm andthe thickness of the imaging element 33 is 0.51 mm. The optical fiber 59has a maximum outer diameter of 0.052 mm. The light guides 57 as thelighting member are placed at, for example, two respective places inpoint symmetry.

Sixteenth Configuration Example

FIG. 36 is a perspective view of the tip portion 15 of the endoscope 11according to the present embodiment in which the imaging element 33 andthe sheath 61 are substantially in contact with each other and the fourcorners of the imaging element 33 are not chamfered. FIG. 37 is aperspective view in which the sheath 61 of the endoscope 11 illustratedin FIG. 36 is seen through. FIG. 38 is a front sectional view includingthe imaging element 33 of the endoscope 11 illustrated in FIG. 36. Thefront sectional view shows the appearance of the section perpendicularto the axial direction through the optical axis or the lens center.

FIG. 29 described above can also be used as a plan sectional view of theendoscope 11 illustrated in FIG. 36. When FIG. 29 is applied to thepresent configuration example, the thickness of the mold resin withwhich the gap between the imaging element 33 and the sheath 61 is filledis reduced as the gap is narrowed based on the substantial contactbetween the imaging element 33 and the sheath 61.

Description of the configuration of the present configuration examplethat is similar to those of the configuration examples described abovemay be omitted or provided in a simplified manner.

The endoscope according to the sixteenth configuration example isprovided with a single lens (such as the lens 93) that has asubstantially quadrangular outer shape (such as a square shape and arectangular shape) in the direction perpendicular to the optical axis orthe lens center. The endoscope 11 is provided with the imaging element33 that has a substantially quadrangular outer shape (such as a squareshape and a rectangular shape) in the direction perpendicular to thelens center with the length of its one side being equal to the length ofone side of the single lens. The endoscope 11 is provided with theelement cover glass 43 covering the imaging surface 41 of the imagingelement 33 and having the same outer shape as the imaging element 33 inthe direction perpendicular to the lens center. The endoscope 11 isprovided with the sheath 61 placed coaxially with respect to the lenscenter, surrounding the respective outside surfaces of the single lens,the element cover glass 43, and the imaging element 33, and having acircular outer shape. The sheath 61 is substantially in contact with theimaging element 33.

This endoscope 11 is assembled as follows. Specifically, for example, acamera Assy is completed by assembly of the lens 93, the imaging element33, and the transmission cable 31. Then, the light guide 57 includingthe plurality of optical fibers 59 is placed along at least one side ofthe members such as the imaging element 33, the element cover glass 43,the lens 93, and the objective cover glass 91 and fixed to the side bypasting or the like. Then, the covering with the sheath 61 is conductedfrom the outside of the light guide 57 fixed to the camera Assy.Finally, the gaps between the fiber Assy and light guide 57 and thesheath 61 are filled with the mold resins 145 and 146, which results infixing without a gap.

Herein, being “substantially in contact” member that a tiny gap (void)may be present or absent at the position where the imaging element 33and the sheath 61 are at the shortest distance from each other, that is,between the four corners (corner portions) of the imaging element 33 andthe sheath 61.

In a case where the tiny void is present, assembly performanceimprovement is available during endoscope assembly. In other words, whenthe camera Assy and the fiber Assy are covered from the outsides withthe sheath 61 during the assembly of the endoscope 11, hindrance to asmooth assembly of the sheath 61 attributable to the sheath 61 beingcaught by the imaging element 33 of the camera Assy or the fiber Assycan be suppressed.

In a case where the tiny void is absent, the four corners of the imagingelement 33 and the sheath 61 are in contact with each other. In thiscase, a heat-shrinkable tube is used as the sheath 61. Gaps are presentbetween the four corners of the imaging element 33 and the sheath 61before, for example, heating in the assembly process described above.Once the sheath 61 is heated after the covering with the sheath 61 orthe filling with the mold resin 146, the sheath 61 contracts and thefour corners of the imaging element 33 and the inner peripheral surfaceof the sheath 61 abut against each other. The state of the abutting(such as whether the imaging element 33 and the sheath 61 are to beslightly in contact with each other or to be put into a state where theyare completely in contact with each other) may be adjusted depending on,for example, the degree to which the sheath 61 is heated.

When the heat-shrinkable tube is used as described above, the diagonallength of the imaging element 33 and the length of the diameter of thesheath 61 can be substantially equal to each other. Then, the diameterof the tip portion 15 of the endoscope 11 can be further reduced.

The number of the outside surfaces that are present in the imagingelement 33 is equal to the number of individual sides of the imagingelement 33, and thus the number is four in a case where the imagingelement 33 has a quadrangular outer shape.

A holder that holds the lens 93 and the imaging element 33 can beomitted from the endoscope 11 according to the sixteenth configurationexample. Accordingly, a space that is equivalent to the holder can beremoved. In addition, since the imaging element 33 and the sheath 61 aresubstantially in contact with each other, the diagonal length of thequadrangular sectional shape in a front view of the imaging element 33and the length of the diameter of the circular section in a front viewof the sheath 61 are substantially equal to each other, whichcontributes to a reduction in the diameter of the tip portion 15 of theendoscope 11.

Despite the absence of the holder, the sheath 61 is substantially incontact with the four corners of the imaging element 33 in the endoscope11. Accordingly, the imaging element 33 is held with the position of theimaging element 33 fixed at a predetermined position in the planedirection perpendicular to the axial direction through the optical axisor the lens center of the lens 93. Since the surrounding by the sheath61 covers the outside surfaces of the imaging element 33, the elementcover glass 43, and the lens 93, strength improvement is available inthe outer peripheries of the imaging element 33, the element cover glass43, and the lens 93. Accordingly, an unintended deformation of the tipportion 15 can be suppressed even if an external force is generated withrespect to the tip portion 15 of the endoscope 11.

With the endoscope 11 described above, both a reduction in the size ofthe endoscope 11 and an improvement in robustness in the tip portion 15can be achieved.

In the endoscope 11, the sheath 61 and the lens 93 may be substantiallyin contact with each other as well while the sheath 61 is substantiallyin contact with the imaging element 33. This allows the position of theimaging element 33 and the sheath 61 to be fixed at predeterminedpositions in the plane direction perpendicular to the axial directionthrough the optical axis or the lens center of the lens 93.Alternatively, the sheath 61 and the lens 93 may be substantially incontact with each other instead of the sheath 61 being substantially incontact with the imaging element 33. The sheath 61 may also besubstantially in contact with one or both of the element cover glass 43and the objective cover glass 91.

In the endoscope 11, the objective cover glass 91 is placed further onthe objective side than the lens 93 and it has the same outer shape asthe lens 93 in the direction perpendicular to the lens center. Theobjective cover glass 91 and the sheath 61 are disposed substantially onthe same plane on the insertion tip surface 135 of the tip portion 15including the objective cover glass 91 and the lens 93.

In other words, the sheath 61 extends up to the tip of the tip portion15 outside the lens 93, the element cover glass 43, and the imagingelement 33. As a result, surrounding by the sheath 61 continues from theimaging element 33 on the back face side to the objective cover glass 91at the tip of the tip portion 15, and thus robustness improvement isavailable up to the tip of the tip portion 15.

The endoscope 11 may also be provided with the lighting member (such asthe light guide 57) placed along the lens center and inserted betweenthe respective outside surfaces of the lens 93 and the imaging element33 and the inner peripheral surface of the sheath.

This leads to member placement density improvement in the tip portion 15of the endoscope 11 because the space resulting from the difference inshape between the part of the sheath 61 that has a circular section inthe front view and the parts of the lens 93 and the imaging element 33that have a quadrangular sectional shape in the front view can be usedfor the placement of the light guide 57. As a result, the subject can beilluminated with a useless space suppressed.

In addition, the space between the outside surface of each of the lens93 and the imaging element 33 and the inner peripheral surface of thesheath 61 in the endoscope 11 may be filled with a mold portion (such asthe mold resins 145 and 146). The mold resins 145 and 146 according tothe twelfth configuration example are not illustrated in FIGS. 36 and37. Still, it is filled with the mold resins 145 and 146 as in FIG. 28.

As a result, the robustness of the endoscope 11 can be maintained by themold resins 145 and 146, with which the space between the sheath 61 andthe imaging element 33 or the like is filled, with its diameter reducedby the sheath and the imaging element 33 or the like being substantiallyin contact with each other. Since the space between the sheath 61 andthe imaging element 33 or the like is filled without a gap with the moldresin, the waterproofness and dustproofness of the endoscope 11 can beimproved as well.

Seventeenth Configuration Example

FIG. 39 is a perspective view of the tip portion 15 of the endoscope 11according to the present embodiment in which the imaging element 33 andthe sheath 61 are substantially in contact with each other and the fourcorners of the imaging element 33 are chamfered. FIG. 40 is aperspective view in which the sheath 61 of the endoscope 11 illustratedin FIG. 39 is seen through. FIG. 41 is a front sectional view includingthe imaging element 33 of the endoscope 11 illustrated in FIG. 39. FIG.42 is a plan sectional view of the endoscope 11 illustrated in FIG. 39.

Description of the configuration of the present configuration examplethat is similar to those of the configuration examples described abovemay be omitted or provided in a simplified manner.

In FIGS. 39 to 42, the four corners of the imaging element 33 arechamfered and the chamfered corners are illustrated as cut surfaces 221.Cut surfaces at the four corners of the element cover glass 43 areillustrated as cut surfaces 222. Cut surfaces at the four corners of thelens 93 are illustrated as cut surfaces 223. Cut surfaces at the fourcorners of the objective cover glass 91 are illustrated as cut surfaces224.

In comparison to the sixteenth configuration example, the endoscope 11according to the seventeenth configuration example has a shape in whichat least some of the four corners of the quadrangular shape of at leastthe imaging element 33 are cut. Some of the four corners member that thefour angles of the quadrangular shape may be chamfered without exceptionor the number of such chamfered angles may be three or less. Examples ofthe way in which the chamfering is conducted include the methodaccording to the ninth configuration example. In other words, theimaging element 33 may have an octagonal outer shape, a dodecagonalouter shape, or a polygonal outer shape with at least 13 sides.

The diagonal length of the imaging element 33 can be reduced in theendoscope 11 according to the seventeenth configuration example when atleast some of the four corners of the imaging element 33 that has aquadrangular sectional shape in the front view are cut. Because theimaging element 33 and the sheath 61 are substantially in contact witheach other, the diagonal length of the quadrangular sectional shape inthe front view of the imaging element 33 and the length of the diameterof the circular section of the sheath 61 in the front view aresubstantially equal to each other. Accordingly, the length of thediameter of the sheath 61 that is placed on the outermost side of theendoscope 11 can be reduced, and thus the diameter of the endoscope 11can be more reduced than in a case where the four corners of the imagingelement 33 are not chamfered.

The lens 93 in the endoscope 11 may also have a shape in which at leastsome of the four corners of its quadrangular sectional shape in a frontview are cut. Some of the four corners member that the four angles ofthe quadrangular shape may be chamfered without exception or the numberof such chamfered angles may be three or less. Examples of the way inwhich the chamfering is conducted include a method similar to that bywhich the imaging element 33 is chamfered. In other words, the lens 93may have an octagonal outer shape, a dodecagonal outer shape, or apolygonal outer shape with at least 13 sides.

The imaging element 33 and the lens 93 may be chamfered by differentmethods, too. The imaging element 33 and the lens 93 may have differentouter shapes as a result.

The diagonal length of the lens 93 can be reduced in the endoscope 11when at least some of the four corners of the lens 93 that has aquadrangular sectional shape in the front view are cut. In a case wherethe lens 93 and the sheath 61 are substantially in contact with eachother, the diagonal length of the quadrangular sectional shape in thefront view of the lens 93 and the length of the diameter of the circularsection of the sheath 61 in the front view are substantially equal toeach other. Accordingly, the length of the diameter of the sheath 61that is placed on the outermost side of the endoscope 11 can be reduced,and thus the diameter of the endoscope 11 can be more reduced than in acase where the four corners of the lens 93 are not chamfered.

In general, it is more difficult to reduce the size of the imagingelement 33 than to reduce the size of the lens 93. Accordingly, thediagonal length of the imaging element 33 becoming a bottleneck inreducing the diameter of the tip portion 15 of the endoscope 11 isobserved in a case where the diameter of the endoscope 11 is minimized.Accordingly, the imaging element 33 may be chamfered without the lens 93being chamfered in a case where the area of the quadrangular sectionalshape in the front view of the imaging element 33 (non-chamfered area)exceeds the area of the quadrangular sectional shape in the front viewof the lens 93. In this case, a reduction in the diameter of the tipportion 15 of the endoscope 11 is pursued by the diagonal length of thequadrangular sectional shape in the front view of the lens 93 and thelength of the diameter of the sheath 61 being allowed to becomesubstantially equal to each other. In addition, chamfering may also beperformed on both the imaging element 33 and the lens 93 in the casewhere the area of the quadrangular sectional shape in the front view ofthe imaging element 33 exceeds the area of the quadrangular sectionalshape in the front view of the lens 93. Then, the diameter of the tipportion 15 of the endoscope 11 can be more reduced than in a case wherethe imaging element 33 is chamfered without the lens 93 being chamfered.

The area of the quadrangular sectional shape in the front view of theimaging element 33 may fall short of the area of the quadrangularsectional shape in the front view of the lens 93 as well. In this case,the lens 93 may be chamfered without the imaging element 33 beingchamfered. In this case, a reduction in the diameter of the tip portion15 of the endoscope 11 is pursued by the diagonal length of thequadrangular sectional shape in the front view of the imaging element 33and the length of the diameter of the sheath 61 being allowed to becomesubstantially equal to each other. In addition, chamfering may also beperformed on both the imaging element 33 and the lens 93 in the casewhere the area of the imaging element 33 falls short of the area of thelens 93. Then, the diameter of the tip portion 15 of the endoscope 11can be more reduced than in a case where the lens 93 is chamferedwithout the imaging element 33 being chamfered.

The element cover glass 43 and an objective cover glass 44 may bechamfered as is the case with the imaging element 33 and the lens 93.Exemplified in FIG. 42 is a state where the four corners of the imagingelement 33, the element cover glass 43, the lens 93, and the objectivecover glass 91 are chamfered by being cut in the form of the cutsurfaces 221, 222, 223, and 224, respectively.

The number of the optical fibers 59 that are placed in parallel (in arow herein) along each of two parallel sides of the imaging element 33is six in FIG. 40. The number of the optical fibers 59 that are placedin parallel (in a row herein) along each of the four sides of theimaging element 33 is three in FIG. 41. In the present configurationexample, any number can be the number of sides along which the opticalfiber 59 is arranged and the number of the optical fibers 59 arrangedalong each side.

The shapes of the transmission cable 31 in the plan sectional viewillustrated in FIG. 42 including the chamfered imaging element 33 and inthe plan sectional view illustrated in FIG. 29 including thenon-chamfered imaging element 33 differ from each other, but any of theconfigurations can be adopted. In other words, the transmission cable 31illustrated in FIG. 29 may be described in FIG. 42 and the transmissioncable 31 illustrated in FIG. 42 may be described in FIG. 29.

The mold resin 145 extends from the tip of the tip portion 15 up to thesectional position of the imaging element 33 in FIG. 29 whereas the moldresin 145 extends from the tip of the tip portion 15 up to the sectionalposition of the electric wire 45 beyond the imaging element 33 in FIG.42. Any of the configurations can be adopted. In other words, the moldresin 145 illustrated in FIG. 29 may be described in FIG. 42 and themold resin 145 illustrated in FIG. 42 may be described in FIG. 29.

Eighteenth Configuration Example

As illustrated in FIGS. 37 and 40, for example, the endoscope 11according to the eighteenth configuration example is provided with asingle lens (such as the lens 93) that has a substantially quadrangularouter shape (such as a square shape, a rectangular shape, and achamfered quadrangular shape) in the direction perpendicular to theoptical axis or the lens center. The endoscope 11 is provided with theimaging element 33 that has a substantially quadrangular outer shape(such as a square shape and a rectangular shape) in the directionperpendicular to the lens center with the length of its one side beingequal to the length of one side of the single lens. The endoscope 11 isprovided with the element cover glass 43 covering the imaging surface 41of the imaging element 33 and having the same outer shape as the imagingelement 33 in the direction perpendicular to the lens center. Theendoscope 11 is provided with the sheath 61 placed coaxially withrespect to the lens center, surrounding the outside surfaces of thesingle lens, the element cover glass 43, and the imaging element 33, andhaving a circular outer shape. The sheath 61 is substantially in contactwith the imaging element 33. In addition, the endoscope 11 is providedwith the lighting member (such as the optical fibers 59) placed alongthe lens center and inserted between the respective outside surfaces ofthe single lens and the imaging element 33 and the inner peripheralsurface of the sheath 61. The number of the lighting member is at leasttwo. The plurality of lighting member is placed in parallel (in a row,for example) along at least one side of the single lens or the imagingelement 33 (sides H1 to H4, for example).

A holder that holds the lens 93 and the imaging element 33 can beomitted from the endoscope 11 according to the eighteenth configurationexample. Accordingly, a space that is equivalent to the holder can beremoved. In addition, since the imaging element 33 and the sheath 61 aresubstantially in contact with each other with the four corners of theimaging element 33 chamfered or not chamfered, the diagonal length ofthe quadrangular sectional shape in the front view of the imagingelement 33 and the length of the diameter of the sheath 61 aresubstantially equal to each other, which contributes to a reduction inthe diameter of the tip portion 15 of the endoscope 11.

This leads to member placement density improvement in the tip portion 15of the endoscope 11 as the space resulting from the difference in shapebetween the part of the sheath 61 that has a circular section in thefront view and the parts of the lens 93 and the imaging element 33 thathave a quadrangular sectional shape in the front view can be used forthe placement of the light guide 57 (the plurality of optical fibers 59herein). As a result, a useless space in the tip portion 15 can besuppressed in the endoscope 11.

In the endoscope 11, the plurality of optical fibers 59 is not placed inan arbitrary way in the space resulting from the shape difference.Instead, the plurality of optical fibers 59 are arranged in parallelalong at least one side of the lens 93 or the imaging element 33.Accordingly, the number of the optical fibers 59 that can be arranged inthe space of the same size is larger than in a case where the pluralityof optical fibers 59 is placed in an arbitrary way. As a result, thenumber of illuminations increases, which leads to an increase in thebrightness of lighting.

As described above, both a reduction in the size of the endoscope 11 andlighting efficiency improvement can be achieved from the endoscope 11.

Nineteenth Configuration Example

In the endoscope 11 according to the nineteenth configuration example,the plurality of lighting member (such as the optical fibers 59) areplaced in parallel along each of at least two sides of the single lens(such as the lens 93) or the imaging element 33 and are placed in pointsymmetry with respect to the lens center.

In FIGS. 38 and 41, the number of the optical fibers 59 that are placedin parallel (in a row herein) along each of the four sides H1 to H4 ofthe quadrangular sectional shape in the front view of the imagingelement 33 is three. Referring to FIGS. 38 and 41, it can be appreciatedthat the optical fibers 59 are placed at the respective positions ofpoint symmetry with respect to the center of the imaging element 33. Thecenter of the imaging element 33 corresponds to the lens center in thecross section perpendicular to the optical axis or the lens center.

The optical fibers 59 in the endoscope 11 according to the nineteenthconfiguration example are equidistantly placed across the center of theimaging element 33, and thus the object of observation can beilluminated in a uniform manner. Accordingly, uneven illumination by theendoscope 11 can be reduced, the quantity of the light that is obtainedfrom the subject can be equalized in the respective pixels of theimaging element 33, and the pixels can be given a uniform image quality.As a result, the quality of the image of the subject obtained with theendoscope 11 is improved.

Any number can be the number of the optical fibers 59 according to thepresent configuration example. In addition, the optical fibers can beplaced in parallel along any of the sides of the quadrangular shape. Theparallel placement may be performed in a row with respect to at leastone side of the imaging element 33. As long as a space for placement isallowed, the parallel placement may be performed in two or more rows.

FIG. 43 is a drawing illustrating a first modification example of thearrangement of the plurality of optical fibers 59. The number of theoptical fibers 59 that are placed in parallel (in a row herein) alongeach of the four sides H1 to H4 of the quadrangular sectional shape inthe front view of the imaging element 33 is five in FIG. 43.

FIG. 44 is a drawing illustrating a second modification example of thearrangement of the plurality of optical fibers 59. The number of theoptical fibers 59 that are placed in parallel (in a row herein) alongthe two sides H1 and H2 of the quadrangular sectional shape in the frontview of the imaging element 33 is five in FIG. 44. The two sides H1 andH2 in FIG. 44 are sides at positions of point symmetry with respect tothe center of the imaging element 33. The respective optical fibers 59are arranged in point symmetry with respect to the center of the imagingelement 33.

Twentieth Configuration Example

FIG. 45 is a diagram for showing an example of the length of thediameter of the optical fiber 59 of the endoscope 11 according to thepresent embodiment.

The imaging element 33 in the endoscope 11 according to the twentiethconfiguration example has a square outer shape in the directionperpendicular to the lens center. The length of the diameter of thelighting member (such as the optical fiber 59) is 20% or less of thelength of one side of the imaging element 33.

In the endoscope 11 according to the twentieth configuration example,accommodating in a space sp resulting from the difference in shapebetween the part of the sheath 61 that has a circular section in thefront view and the part of the lens 93 that has a quadrangular sectionalshape in the front view can be conducted with consideration given to thelength of the diameter of the optical fiber 59.

Assuming that the length of one side of the imaging element 33 is “a”,the imaging element 33 has a diagonal length of “√2a” in FIG. 45. √A isthe square root of Value A. Accordingly, √2 is the square root of Value2. According to FIG. 45, the four corners of the square sectional shapein the front view of the imaging element 33 are substantially in contactwith an inner peripheral surface 61 a of the sheath 61. Since the sheath61 has a circular outer shape, the length of the diameter of the sheath61 is “√2a”.

In the cross section illustrated in FIG. 45, the space sp is formedbetween the sheath 61 having a circular cross section in the front viewand the imaging element 33 having a square sectional shape in the frontview, which are substantially in contact with each other. In the spacesp, the maximum length of the diameter of the optical fiber 59 isequivalent to a distance d1, which is the distance from the innerperipheral surface 61 a of the sheath 61 to the side H1 of the imagingelement 33 orthogonal to the radial direction of the circular crosssection in the front view of the sheath 61. The distance d1 isrepresented by the following (Equation 1).d1=(√2a−a)/2≅0.2a  (Equation 1)

In other words, the diameter of the optical fiber 59 that can beinserted into the space sp is 20% or less of the length a of one side ofthe imaging element 33.

The length a of one side of the imaging element 33 is, for example, 500μm. The length of the diameter of the optical fiber 59 is, for example,50 μm. In this case, the diameter of the optical fiber 59 becomes 10% ofone side of the imaging element 33 and satisfies (Equation 1) related tothe maximum length d1 of the diameter of the optical fiber 59.

The embodiment has been described above with reference to theaccompanying drawings. It is a matter of course that the presentinvention is not limited to the example. It is obviously conceivablethat various modified or correction examples are available within thescope of the claims depending on those skilled in the art and it isclearly understood that such examples naturally pertain to the technicalscope of the present invention. Elements constituting the embodiment maybe appropriately combined with each other in any form without departingfrom the purpose of the present invention.

The present disclosure is effective as, for example, a small-diameterendoscope with which stray light from lighting member can be preventedwith high-strength fixing of a lens and an imaging element facilitatedand size reduction ensured by space efficiency (that is, memberplacement density) improvement (that is, suppression of a useless space)being allowed in an insertion tip surface.

What is claimed is:
 1. An endoscope comprising: a lens that has aquadrangular outer shape in a direction perpendicular to a center axisof the lens; an imaging element that has a quadrangular outer shape inthe direction perpendicular to the center axis; an element cover glassconfigured to cover an imaging surface of the imaging element; alighting member that is disposed outside at least one side of the lensand extends along the center axis; a light-shielding member that isdisposed between the lens and the lighting member; and an objectivecover glass, wherein the element cover glass is disposed between theobjective cover glass and the imaging element, wherein thelight-shielding member has a first side portion disposed on a first sideof the lens and a second side portion disposed on a second side of thelens, wherein both of the first side portion and the second side portionhave a length equal to or greater than a length from an insertion tipsurface in a tip portion of the endoscope to the imaging surface of theimaging element, wherein the lens and the imaging element are disposedbetween a first end and a second end of the first side portion of thelight-shielding member when viewed from the direction perpendicular tothe center axis, wherein the lens and the imaging element are disposedbetween a first end and a second end of the second side portion of thelight-shielding member when viewed from the direction perpendicular tothe center axis, wherein the light-shielding member includes a frontportion and a back portion that is adjacent to the front portion,wherein the back portion of the light-shielding member has aquadrangular outer shape, wherein an aperture having a quadrangularouter shape is formed in the front portion of the light-shieldingmember, and the objective cover glass is disposed within the aperture,and wherein an outer diameter of the back portion of the light-shieldingmember is less than an outer diameter of the front portion of thelight-shielding member.
 2. The endoscope according to claim 1, whereinthe light-shielding member is a holder coaxially accommodating the lensand the imaging element; and wherein a notch is provided on an outerperipheral surface of the holder and extends in a direction along thecenter axis to place the lighting member thereon.
 3. The endoscopeaccording to claim 1, wherein the light-shielding member is a holdercoaxially accommodating the lens and the imaging element; and wherein athrough-hole is provided between an outer peripheral surface of theholder and one side of the lens and extends in a direction along thecenter axis to place the lighting member therein.
 4. The endoscopeaccording to claim 1, wherein the light-shielding member is comprised ofresin and configured to cover an outside surface of the lighting member.5. The endoscope according to claim 1, wherein the light-shieldingmember is a pipe into which the lighting member is inserted.
 6. Theendoscope according to claim 1, wherein the light-shielding member hasan end surface including both the first end of the first side portionand the first end of the second side portion.
 7. The endoscope accordingto claim 1, wherein the first side portion of the light-shielding memberis separated from the second side portion of the light-shielding member.8. The endoscope according to claim 1, wherein the front portionincludes the first side portion and the second side portion.